Leviticus 7:30-36

His own hands will bring the food offerings to the LORD. He will bring the fat together with the breast. The breast is to be presented as a presentation offering  before the LORD. The priest is to burn the fat on the altar, but the breast belongs to Aaron and his sons. You are to give the right thigh  to the priest as a contribution from your fellowship sacrifices. The son of Aaron who presents the blood of the fellowship offering and the fat will have the right thigh as a portion. I have taken from the Israelites the breast of the presentation offering and the thigh of the contribution from their fellowship sacrifices, and have assigned them to the priest Aaron and to his sons as a permanent portion  , from the Israelites.” This is the portion from the food offerings to the LORD for Aaron and his sons  since the day they were presented to serve the LORD as priests. The LORD commanded this to be given to them by the Israelites on the day he anointed them.  It is a permanent portion throughout their generations.