[Issues in Ijtihād and Taqlīd]2

Answer: Every mujtahid is correct—even if his evidence is shown to
be weak—meaning that the mujtahid who acts upon his ijtihād is correct
in acting upon what he saw as valid, and likewise his followers are
correct in following him; there is no blame upon them before Allah. If we
come to know the weakness of that mujtahid’s evidence and it becomes
clear to us that he erred, this does not affect the validity of his madhhab
nor the correctness of his followers.
The proof of this issue is Allah’s saying:
“And there is no blame upon you for that in which you erred, but [only
for] what your hearts intended.” — [al-Aḥzāb 33:5]
However, it is not permissible for a follower who has come to know
the weakness of that mujtahid’s reasoning to continue imitating him in
that issue.