Redemption of the Firstborn in the Torah
Question
Answer
Hello
There are three different aspects in the laws of firstborns: the firstborn of a human, the firstborn of a pure animal, and the firstborn of a donkey.
The firstborn of a human is redeemed with five selaim, which the father of the child gives to the priest to redeem his son.
The firstborn of a pure animal is given to the priest as a gift. If the firstborn is fit for sacrifice, the priest must offer it and then eat its meat. If the firstborn is not fit for sacrifice, the priest may do with it as he pleases (eat it or sell it).
The firstborn of a donkey is redeemed, and the owner of the donkey must give one lamb as redemption to the priest. If the owner of the donkey does not wish to redeem the donkey, he must kill it by breaking its neck.
Source
Numbers 18:15. Rambam, Laws of Firstborns.