Every firstling of a beast shall be the Lord's That is, every firstling male of a clean beast, as of the cow, sheep, or goat kind, was to be offered in sacrifice; and the blood being sprinkled, and the fat burned on the altar, the flesh of them was to be given to the priests, Numbers 18:17-18.
Related Commentaries of Exodus 13:12
Exodus 13:12
12 That thou shalt set apart unto the LORD all that openeth the matrix, and every firstling that cometh of a beast which thou hast; the males shall be the LORD'S.