Although they say they are Muslims, Wahhabis, are one of the groups who have departed from the Ahl as-Sunnat.

Muhammad Hasan Jan as-Sirhindi al-Mujaddidi (rahmat-Allahi ta'ala 'alaih) wrote in his
'Al Usul al-arba'a fi tardid'l-wahhabiyya , at the end of its second part:

The Wahhabis and other la-madhhabi people cannot comprehend the meanings of majaz[1] and isti'ara' (metaphor). Whenever somebody says that he did something, they call him a polytheist or a disbeliever though his expression is a majaz. However, Allahu ta'ala declares in many ayats of Qur'an al-karim that He is the Real Maker of every act and that man is the majazi maker. 
In the 57 th ayat of Surat al-Anam and in Surat Yusuf, He says: "The decision (hukm) is Allahu ta'ala's alone," that is, Allahu ta'ala is the only Decider (hakim). 
In the 64 th ayat of the Surat an-Nisa', He says: "They will not be believers unless they make thee (the Prophet) judge (yuhakkimunaka) of what is in dispute between them." The former ayat states that Allahu ta'ala is the only Real Hakim, and the latter states that man can be metaphorically referred to as a hakim.
Every Muslim knows that Allahu ta'ala alone is the One who gives life and takes life away, for He declares: "He alone gives and takes life," in the 56 th ayat of the Surat Yunus, and, "Allahu ta'ala is the One who makes man dead at the time of his death," in the 42nd ayat of the Surat az-Zumar. In the 11 th ayat of the Surat as-Sajda, He says as a majaz: "The angel who is appointed as the deputy to take life takes your life."
Allahu ta'ala alone is the One who gives health to the sick, for the 80 th ayat of Surat ash- Shu'ara states: "When I become sick, only He gives me recovery." He quotes 'Isa ('alaihi 's-salam) in the 49 th ayat of the Al-i 'Imran sura as saying: "I heal him who is blind and baras[38], and I bring the dead back to life by Allahu ta'ala's permission." The One who gives a child to man is actually He; the 18 th ayat of the Surat Mariam states [the Archangel] Jabrail's ('alaihi 's-salam) majazi words, "I will give you a pure son."
The real owner of man is Allahu ta'ala. 
The 257 th ayat of the Surat al-Baqara states this openly: "Allahu ta'ala is the Wali (Protector, Guardian) of those who believe." And by saying, "Allahu ta'ala and His Prophet ('alaihi 's-salam) are your walis," and "The Prophet protects the believers more than they protect themselves," in the 56 th and 6 th ayats of Suras al-Ma'ida and al-Ahzab, respectively, He means that man, too, though symbolically, is a wali. Similarly, the real helper is Allahu ta'ala, and He also calls men 'muin' (helper) metaphorically. He says in the third ayat of the Surat al-Ma'ida: "Help one another in goodness and piety (taqwa)." Wahhabis use the word 'mushrik' (polytheist) for those Muslims who call somebody an 'abd (servant, slave) of someone other than Allahu ta'ala, for example, ''Abd an-Nabi' or ''Abd ar-Rasul'; however, in the 32 nd ayat of Surat an-Nur, it is declared: "Give in marriage your unmarried women and those pious ones among your slaves and female slaves." 

The Real Rabb (Trainer) of men is Allahu ta'ala, but someone else can also be called 'rabb' metaphorically; in the 42 nd ayat of the Surat Yusuf is said, "Mention me in the presence of your rabb."

'Istighatha' is what the Wahhabis oppose most: 'to ask help or protection of someone other than Allahu ta'ala,' which they call polytheism. In fact, as all Muslims know, true istighatha is only for Allahu ta'ala. However, it is permissible to say metaphorically that one can do istighatha for someone, for, it is declared in the 15 th ayat of Surat al-Qassass: "People of his tribe did istighatha for him against the enemy." A hadith ash-Sharif says, "They will do istighatha for Adam ('alaihi 's-salam) at the place of the Mahshar." A hadith ash-Sharif written in Al-hisn al-hasin, says, "He who needs help should say, 'O Allahu ta'ala's slaves! Help me!' " This hadith ash-Sharif commands one to call for help from someone not near him"
 Foot Notes:

[1] Majaz is the use of a word not in its usual or obvious literal meaning but in a sense connected to its meaning. When a word special to Allahu ta'ala is used for men in a majazi (figurative, symbolic) sense, the Wahhabis take it in its literal meaning and call the one who uses it symbolically a polytheist and disbeliever; they are unaware that such words are used for men in symbolical senses in Qur'an al-karim and Hadith ash-Sharif.

[2] Al-usul al-arba'a fi tardid al-Wahhabiyya (in Persian), end of the second part, India, 1346 (1928 A.D.); photographic reproduction, Istanbul, 1395 (1975 A.D.). This book was written by Muhammad Hasan Jan Sahib, one of the grandsons of hadrat Imam Rabbani (Shaykh Ahmad Sirhindi) rahmatullahi ta'ala alaihima'. The author, Jan Sahib, refutes the Wahhabis and other la-madhhabi people also in his Arabic work Tariq an-najat, India, 1350 (with Urdu translation); photographic reproduction, Istanbul, 1396 (1976 A.D.).
( The author, passed away in Hyderabad, Pakistan, in 1349 A.H. (1931)

http://www.hizmetbooks.org/Sunni_Path/suwahhab.htm

Who are Ahlu Sunnah? (Noorul Ulama M.A.Usthad)

" Rasulullah ('alaihi 's-salam) declared, while telling about what will happen to his umma in future:  
“The Sons of Israil parted into 72 nations. And my umma will part into 73 groups. Of them, only one will be saved, and all others will go to Hell.”
 As-Sahabat al-kiram upon hearing this, asked, 'Oh Rasul-Allah! Which is that?' He declared, 'They are those who follow my and my Sahaba's path.'
This hadith ash-Sharif was reported from 'Abdullah  ibn 'Umar (radi-Allahu 'anh).
As reported from Muawiya (radi-Allahu 'anh) 
by Imam Ahmad and Abu Dawud, Rasulullah ('alaihi 's-salam) declared, 'Of them, 72 are in Hell, and the remaining one is in Paradise. And this is one jamaat.'
This hadith ash-Sharif is also quoted in the chapter on 'I'tisam' of the book Mishkat.
 Oh Muslims! We must search and find this single community of salvation mentioned in this hadith and their beliefs which cause entrance to Paradise and should beware of heretical groups who oppose these beliefs! In this way, we shall endeavor to get saved from the Hell fire and flame!
Hadrat Ghawth al-azam 'Abd al-Qadir al-Geilani (QS)explained the former hadith and the word 'jamaat' in the latter hadith in these words: 'The believer (Mumin) should adapt himself to the Sunnat and to the Jamaat. The Sunnat is the way shown by Rasulullah ('alaihi 's-salam). The Jamaat is composed of the things done unanimously by as-Sahabat al-kiram who lived in the time of the four caliphs called Khulafa' ar-rashidin. A Muslim must prevent the multiplication of the men of bidat and be away from them and should not greet them. Ahmad Ibn Hanbal, the imam of our madhhab, said that greeting a man of bidat meant loving him since it had been declared in a hadith ash-Sharif, "Disseminate [your] greeting (salam)! Love one another in this way!" ' These are written on the 90th page of Gunyat at-talibin.
Great alim Ahmad ibn Hajar al-Haitami(rah), the last muhaqqiq, wrote on this subject in detail on page 149 of his work Sawa'iq al-muhriqa, where he said, 'Those who dissent from the Ahl as-Sunnat faith are called mubtadi'. They began to come forth in the first century [of Islam].'
"Hadrat Ibn Hajar al-Haitami said in his work Fat'h al-jawad, 'Mubtadi' is the person who does not have the faith (itiqad) conveyed unanimously by Ahl as-Sunnat. This unanimity was transmitted by the two great imams Abu 'l-Hasan al-Ashari and Abu Mansur al-Maturidi and the 'alims who followed their path.' On the 205th page of the book Al-fatawa al-hadithiyya, it is written, 'Man of bidat means one whose beliefs are different from the Ahl as-Sunnat faith. The Ahl as-Sunnat faith is the faith of Abu 'l-Hasan al-Ashari, Abu Mansur al-Maturidi and those who followed them. One who brings forth something which is not approved by Islam becomes a man of bidat.'
 
Shafi'i alim Ahmad Shihab ad-din Kalyubi al-Misri (Rah)wrote on the fourth volume of his marginalia to the book Kanz ar-raghibin: 

'One who departs from what Abu 'l-Hasan al-Ashari(RA) and Abu Mansur al-Maturidi (RA) reported is not Sunni. These two imams followed the footprints of Rasulullah (SallallahuAlaihiwasallam) and his Sahaba(RA).'

[Shaykh Abu Ahmed AbdulQadir Malibari(Noorul Ulama M.A.Usthad)]

73 Sects_Imam-i Rabbani Shaykh Ahmed Sirhindi(qs)

Imam-i Rabbabni Mujaddid e Alf Sani(Reviver of 2nd Millenium of Islam)Shaykh Ahmad Sirhindi an- Naqshbandi(Quddisa Sirrahu) (d.1034.AH.Sirhind Shareef.Punjab.India)
wrote in his Maktubar Shareef [THIRD VOLUME, 38th LETTER]
"It is declared in a hadith that this Ummat will part into seventy-three groups, seventy-two of whom will go to Hell. This hadith informs that the seventy-two groups will be tormented in the fire of Hell. It does not inform that they will stay in torment eternally. Remaining in the torment of Hell-fire eternally is for those who do not have iman. That is, it is for disbelievers. The seventy- two groups, on account of their corrupt belief, will go to Hell and will burn as much as the corruptness of their belief. One group, the seventy-third, will be saved from Hell-fire because their belief is not corrupt. If among the members of this one group there are those who committed evil deeds and if these evil deeds of theirs have not been forgiven through tawba or shafaat, it is possible that these, too, will burn in Hell as much as their sins. All of those who are in the seventy-two groups will go to Hell. But none of them will remain in Hell eternally. Not all of those who are in this one group will go to Hell. Of these only those who have committed evil deeds will go to Hell. The seventy-two reported groups of bidat, which will go to Hell, should not all be called "disbelievers", because they are Ahl-i Qibla.
However, of these people, the ones who disbelieve those Islamic tenets that are indispensable to be believed, as well as those who deny those rules of the Shariat which every Muslim has heard and knows become disbelievers. The savants of the Ahl as-sunnat declare: "If a Muslim's statement signifies a hundred meanings ninety-nine of which causing disbelief and one showing that he is a Muslim, it is necessary to take this one meaning, thus saving him from the state of disbelief." Allahu ta'ala knows the truth of everything. His Word is the most reliable word."
[Translated by Shaykh Huseyn Hilmi Isik.Rah.d.1422.Ah.Istanbul.Turkey]
http://www.hizmetbooks.org/Endless_Bliss_Third_Fascicle/bliss3_2.htm

TheDivisions in the Ummah:

The famous Sahabi Hudhayfah ibn al-Yaman(RA) said, "People used to ask the Prophet (sallallahu alayhe wa sallam) about good things, but I used to ask him about bad things because I was afraid that they might overtake me. I said, 'OMessenger of Allah, we were lost in ignorance (Jahiliyyah) and evil, then Allah brought this good (i.e. Islam). Will some evil come after this good thing?' He said, 'Yes' I asked, 'And will some good come after that evil?'
He said, 'Yes, but it will be tainted with some evil' I asked, 'How will it be tainted?' He said, 'There will be some people who will lead others on a path different from mine. You will see good and bad in them.
I asked,'Will some evil come after that good?' He said, 'Some people will be standing and calling at the gates of Hell; whoever responds to their call, they will throw him into the Fire.' I said, 'O Messenger of Allah, describe them for us.' He said, 'They will be from our own people, and will speak our language.' I asked, 'What do you advise me to do if I  should live to see that?' 
He said, 'Stick to the main body (jama'ah) of the Muslims and their leader (Imam). I asked, What if there is no main body and no leader?' He said 'Isolate yourself from all of these sects,even if you have to eat the roots of trees until death overcomes you while you are in that state.'"
-"...By Him in Whose hand is my soul, my Ummah will split into seventy-three sects: one will enter Paradise and seventy-two will enter Hell." Someone asked, "O Messenger of Allah,who will they be?" He replied, "The main body of the Muslims(al-Jama'ah)."
'Awf ibn Malik(RA) is the only one who reported this Hadith, and its isnad is acceptable.

-"...Verily the Israelites were divided into 72 sects but my people will be divided into 73 sects, all of them will be in the fire except one.' The companions asked. 'Who are they O Messenger of Allah,' Holy Prophet (pbuh)said. `They are those who will be like me and my companions.’ (Tirmidhi -Kitabul Eeman)

Sects in Islam_Allah,the Almighty's Warning

The Holy Qur’an:
Surah Al An’am
(Verse 159)
A well known scholar:
“Surely, those who have made divisions in the irreligion and turned into factions, you have nothing to do with them. Their case rests with Allah alone; then He will tell them what they have been doing. [I591

From his Commentary:

“This Verse carries a general address included wherein are the Disbelievers of Arabia, the Jews and Christians and Muslims, all of them. Addressing them, stated there is the sad end of those who turn away from the straight path of Allah and the instruction given to the Holy Prophet SAWS is that he should have nothing to do with those who take to the ways of error. Then, out of these, there are those  Ways of error which take one in a direction totally opposite to what the straight path is, such as the ways of the disbelievers, polytheists and the people of the Book.
Then, there are other ways too, which do not, though,take one all the way in the opposite direction, but misguide them any way by pulling them away from the straight path and putting them on ways to the rightand left. These are ways of 'doubts' and 'innovations' in the true and settled faith(Shubhii and Bid'ii).
 They too lead one astray.
So, it was said: (Surely, those who have made divisions in their religion and turned into factions, you have nothing to do with them. Their case rests with Allah alone; then He will tell them what they have been doing).
In this verse, made clear first was that the Messenger of Allah was free of any responsibility concerning those who land themselves into the ways of error. The noble Prophet, may the blessings of Allah, and
Peace be upon him, had nothing to do with them. Then,they were given the notice of warning that their case was, sufficient to say,in the hands of Allah Ta'la, and it was He who would punish them on the day of Qiyamah”.
The Holy Prophet (saws) has said:
“The Bani Isra'il had split into seventy two sects. My Ummah will break up into seventy three sects - all of them will go to Hell, except one. The Sahabah asked about the group which would be soblessed with salvation. He (Saws) said:’(ma ana 'alaihi wa ashabihi)”
It is this narration from Sayyidna ibn 'Umar (RA), has been reported by Tirmidhi and  Abu Dawud

According to Tafsir Mazhari, 'Jama'ah' in this Hadithmeans 'the Jama'ah of Sahaba' that is, the collective body or group of thenoble Companions of the Holy Prophet Saws. The reason is thatAllah Ta'ala sent our master, Muhammad al-Mustafa saws asHis Rasul and gave him the Qur'an, and blessed him with another(kind of) Wahy (revelation) - which is called the Hadith orSunnah. Then, there are many difficult or brief or ambiguous verses in theQur'an. For theirTafsir or explanation, Allah Ta'ala promised that Heshall have these clarified through His Rasul.
So, the Holy Prophet saws explained the difficulties and ambiguities of the Qur'an and groomed his direct disciples, that is, the Sahabah into the many modes of his Sunnah through his  word and deed. Therefore, the conduct of the Sahabah as a major collective entity is in itself the statement and the explanation of the Divinely-ordained Shari'ah of Islam.
Therefore, it is the good fortune of a Muslim that he or she should follow the Kitab of Allah and the Sunnah of the Rasa of Allah – and whenever one faces a doubt in the meaning of an 'Ayah of the Qur'an or the sense of a Hadiith, one should go by the meaning and sense preferred by the noble Sahabah.
Unfortunately, as a result of people ignoring this sacrosanct rule of conduct, Islam had to see the emergence of different sectswhich would set aside the proven conduct and explanations of the Sahabah and take the liberty of saying what they wished and declare it to be the very meaning of the Qur'an and Sunnah. These are the ways of error the Holy Qur'an has repeatedly warned against and the Holy Prophet (swas)  has emphatically prohibited it throughout his blessed life, at times, even castigated those acting against this rule with curse.
Imam Ibn Kathir(Rah) wrote:
Allah says;
“Verily, those who divide their religion and break up into sects,you have no concern with them in the least.”
Mujahid, Qatadah, Ad-Dahhak and As-Suddi said that;  this Ayah was revealed about the Jews and
Christians.
Al-Awfi said that Ibn Abbas commented,  (Verily, those who divide their religion and
break up into sects...),
"Before Muhammad SAWS was sent, the Jews and Christians disputed and divided into sects. When Muhammad SAWS was sent, Allah revealed to him
 (Verily,those who divide their religion and break up into sects, you have no concern with them in the least).
It is apparent that this Ayah refers to all those who defy the religion of Allah,or revert from it. Allah sent His Messenger with guidance and the religion of truth so that He makes it victorious and dominant above all religions. His Law is one and does not contain any contradiction or incongruity. Therefore, those who dispute in the religion,  (...and break up into sects), religious sects, just like those who follow the various sects, desires and misguidance - then Allah has purified His Messenger from their ways.
In a similar Ayah, Allah said,
He (Allah) has ordained for you the same religion which He ordained for Nuh, and that which We have revealed to you. (42:13)
A Hadith reads,
“We, the Prophets, are half brothers but have one religion. This,indeed, is the straight path which the Messengers have brought and which commands worshipping Allah alone without partners and adhering to the Law of the last Messenger whom Allah sent. All other paths are types of misguidance, ignorance, sheer opinion and desires; and as such, the Messengers are free from them.
Allah said here, (You have no concern with them in the least...).
Allah's statement,
(Their affair is only with Allah, Who then will tell them what they used to do.) is similar to His statement, Verily, those who believe, and those who are Jews, and the Sabians, and the Christians, and the Majus, and those who worship others besides Allah; truly, Allah will judge between them on the Day of Resurrection. (22:17).