Petter chamor

The Petter Chamor (פטר חמור) or Redemption of the firstborn, is a mitzvah in Judaism in which a male firstborn (bechor) donkey is redeemed by the owner of the donkey, who gives a lamb or kid to a Kohen. The lamb is not required to be firstborn.

The mitzvah applies to the firstborn male offspring of a Jewish-owned donkey. The donkey retains a level of holiness and is forbidden for work. The redemption transfers the holiness to another animal, such as a cow, goat or sheep, so that the donkey can be used for work. The other animal is then given to a Kohen who usually eats it. The ceremony is similar to the redemption of a firstborn male, a pidyon haben when a month-old male child is redeemed with silver coins given to a Kohen.

The mitzvah, albeit rare in modern times, is listed as an "obligation of the body" and thus applies in the diaspora as well as the Land of Israel.