Is it obligatory to fulfill a vow to lose weight after a friend's pregnancy, given that the original intention of the vow is not remembered, and is it permissible to postpone it until after childbirth or visiting the friend without fulfilling the condition of the vow?

If the wording of the vow is explicitly stated, it becomes binding according to the Hanbalis—whether said in jest or seriously—and must either be fulfilled or expiated with an oath. The majority of scholars do not consider it binding. It is more prudent to adopt the view of the Hanbalis; thus, if you do not fulfill the vow, you must offer an expiation for an oath.