Answered by Shaykh Amjad Rasheed
Why is seeking out dispensations’ corruption?

In the Name of Allah, Most Merciful and Compassionate
Before explaining the legal reason for this, let us define seeking out dispensations.’ It is defined by the scholars of the fundamentals of jurisprudence (usul al-fiqh) as: Seeking out the easiest of positions from each school.
It is prohibited to systematically seek out dispensations according to the sounder position, as mentioned in Jam` al-Jawami` and other works of fundamentals.
Among those who deemed seeking out dispensations’ to be corruption (fisq) was Imam Ahmad (Allah be pleased with him), as mentioned by Imam Zarkashi in his al-Bahr al-Muhit (6.325). Zarkashi also quoted Imam Awza`i (Allah be pleased with him) as saying, “However seeks out the strange opinions of the scholars will [eventually] step out of Islam.”
Imam Zarkashi narrated a story, on the authority of Ibn Surayj, through which the underlying legal reason (`illa) behind the prohibition of seeking out dispensations’ may be understood:
“Ibn Surayj said, I heard Qadi Isma’il say: I entered upon [the Caliph] Mu`tadid and he gave me a book. When I looked in it, I found that it had gathered the dispensations from the slips of the ulema and the positions of some ulema. I told him: Whoever wrote this is bereft of religion (zindiq). Mu`tadid said: Are the narrations not sound? I said: The narrations are according to their narrators. However, the scholars who [f: erred and] permitted intoxicants did not permit temporary marriage. And those who [f: erred and] permitted temporary marriage did not permit intoxicants. Every scholar errs. And whoever gathers the errors of scholars and then adopts them will lose their deen.
So Mu`tadid commanded that the book be burned.”
Amjad Rasheed.
(Translated by Faraz Rabbani)
Faraz adds:
See also:
Seeking Out Dispensations & Following Another School – From Sheikh Nuh Keller’s Reliance of the Traveller
Objection to Following Another Madhhab Answered
When can I follow another madhhab? The way of fatwa and the way of taqwa