Which Math-hab did Ibn Tayyimah, Ibn Qayyim, Shaikh Uthaymeen and Shaikh Bin Ba'z follow?

Answer

Ibn Taimiyyah followed none of the Four Math-habs of the Ahlus Sunnah Wal Jama'ah. Besides the Hanafi, Maaliki, Shaafi' and Hambali Math-habs, there is the Nafsaani math-hab. This is the math-hab of vain desire, self-opinion and deviation. He initiated his own nafsaani math-hab. Ibn Qayyim was his student, hence followed him (Ibn Taimiyyah). The other two are Salafis. They don't follow any of the Four Math-habs. They were freelancers, flitting from Math-hab to Math-hab to suit their opinions.