The World Federation One Stop Fiqh

Ruling 2681

If a person vows to give a sheep to the poor as alms, or to give it in the name of one of the Infallible Imams (ʿA), then in the event that it gives milk or gives birth before it is given to fulfil the vow, the milk/lamb belongs to the person who made the vow unless his intention [when he made the vow] included the milk/lamb. However, the sheep’s wool and the amount of weight it gains are part of the vow.