What is the ruling on vowing to slaughter for the poor, contingent upon recovery, and is it permissible to eat from it or feed friends in a foreign land?

A vow (nadhr) is when a Muslim obligates himself to do something that he was not previously obligated to do by Islamic law. A conditional vow is disliked because it does not avert anything; rather, it merely extracts from the miserly, and it may increase obligations that a person might not be able to fulfill. However, if the condition is met, fulfilling the vow becomes obligatory due to the generality of the texts, including the Prophet's (peace be upon him) saying: "Whoever vows to obey Allah, let him obey Him. And whoever vows to disobey Him, let him not disobey Him." As for the one who made the vow eating from his vow or feeding his friends from it, it depends on his intention.