What is the ruling on eating from a sacrificial animal that was vowed to be slaughtered if a specific event occurs?

Question:
May Allah reward you, Honorable Shaykh. This questioner says: I vowed to slaughter a sacrificial animal if a certain matter came to pass. I fulfilled my vow, but I ate from this sacrificial animal. The question is: does this vow suffice, or must I slaughter another one?

Answer:
If you vowed to slaughter a sacrificial animal to give in charity to the poor and needy, this is a vow of obedience. This is a vow of obedience, and you are required to fulfill it. You may not eat from it unless you made an exception. If you said, “and I will eat from it,” that is different. But if you did not make an exception, you must distribute it to the needy and the poor, because this is a vow of obedience. So do not eat anything from it, because what you eat reduces the vow. Do not eat from it if your intention is to give it in charity to the needy. However, if your intention was to slaughter it for your relatives and brothers, then you have a choice between fulfilling it and paying the expiation for an oath, because this is a permissible vow. When a person vows something permissible, he has a choice between fulfilling it and paying the expiation for an oath.