Must one fulfill a vow to fast on Thursday if the vow was modified to be conditional on achieving first place in the school, while only first place in the class was achieved?

A vow to obey Allah, such as fasting on a Thursday to achieve first place in class, must be fulfilled once the condition is met, for the Prophet, peace and blessings be upon him, said: "Whoever vows to obey Allah, let him obey Him." It is not permissible to retract a vow; it is binding and enforceable. As for the second vow related to ranking first in the school, nothing is required from it due to the condition not being met.

If the vow was to fast on any Thursday, it is obligatory to fulfill it. If it was specified for a particular Thursday that has passed, then it must be made up along with an expiation for breaking an oath. Vowing is disliked in Sharia despite the obligation to fulfill it, because it does not avert anything and it is a means by which something is extracted from the miserly.