How to Weigh Scholars' Opinions
8-4-2003 | IslamWeb
Question:
In my previous question I asked about Muhammad Ibn Abdul Wahhab and received an answer that confused me again. The Muslim world is divided into two opinions about this person's reality. Of course, it's very difficult for me to believe one group and ignore the other one because the only thing I can do is to read about this person. In this question I would like to know one thing. As far as I know Muhammad Ibn Abdul Wahhab says that people of Tariqat, in particular adherents of Silsila-I Naqshbandiya, Silsila-i Qadiriyya, are all Bid'at holders. Has Muhammad Ibn Abdul Wahhab said so? Then, I am very sorry but I can in no way accept the fact that people like Salman Farsi , Ja'fari Sadiq , Bayazid Bistami , Yusuf Hamadani , Abduhaliq Gighduvani , Farididdin Attar , Bahauddin Naqshband , Imam Rabbani , Imam Ma'sum , Muhammad Zahid Kotku , Abdul Hakim Arwasi are all Bid'at holders. This is impossible. And yet, Imam Ghazzali , Hasan Basri , Abdul Qadir Ghillani , Ibn Arabi are also among those who practiced Tariqat. How can I admit teaching of Ibn Taymiyya and Muhammad Ibn Abdul Wahhab and ignore those great scholars?
Answer:
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad 
is His slave and Messenger.
Some of the people you mentioned are known for their piety and knowledge while others are not known at all. Then, it is natural to find righteous people and devious people; some people on the right way and others going astray.
It is proved in the Prophetic Hadeeth that: “Jews were divided into seventy-one or seventy-two groups; and Christians were divided into seventy-one or seventy-two groups; and my Ummah (Muslims) will be divided into seventy-three groups.”
Another narration adds: “All of them (the latter) will be in Hellfire except one group.” [Ahmad, Abu Daawood, At-Tirmithi and Ibn Maajah] And it is a sound Hadeeth.
In At-Tirmithi’s narration, the Prophet's Companions asked: “O prophet of Allah, who will be the saved sect?’ He replied: ‘Those who will remain on the path which I and my Companions are on today.’”
As a rule, the Quran and the Prophetic Sunnah are the only competent authority in case of difference as stated in the Quran. Allah Says (what means): {O you who have believed, obey Allah and obey the Messenger and those in authority among you. And if you disagree over anything, refer it to Allah and the Messenger, if you should believe in Allah and the Last Day. That is the best [way] and best in result.} [Quran 4:59]
Imam Al-Qurtubi 
said in his Tafseer (interpretation of the Quran): “The above-verse means that Muslims (in case of disagreement concerning some issues) are required to follow the ruling as stated in the Quran or as practiced by His Prophet during his life or by looking into his Sunnah after his death. This is the saying of Al-A'mash and Qataadah, and it is the correct understanding. Then, whoever does not believe in the above-stated in the verse is, in fact, with unsteady faith.”
In addition to that, nobody is infallible except Prophets and infallibility is part and parcel of Prophethood. In other words, all people, except Prophets, are subject to error; i.e., we can follow some of their correct opinions and refuse others.
Therefore, we weigh each and everyone's opinions with the revelation (The Quran and Sunnah). Then, if we do not find contradiction with the revelation, we accept it; otherwise, we refuse it. For example, if someone says: 'so and so knows al-Ghayb (the Unseen)', we directly refuse such a saying since it contradicts the revelation, and the sayer becomes a disbeliever.
For more benefit on the Ummah (Muslim nation) splitting into 73 sects, please refer to Fataawa 393448, 12682, 81638, 82163, 33503, and 322.
Allah knows best.