First-born, Redemption of From the beginning the office of the priesthood in each family belonged to the eldest son. but when the extensive plan of sacrificial worship was introduced, requiring a company of men to be exclusively devoted to this ministry, the primitive office of the first-born was superseded by that of the Levites (Numbers 3:11-13), and it was ordained that the first-born of man and of unclean animals should henceforth be redeemed (18:15).
The laws concerning this redemption of the first-born of man are recorded in Exodus 13:12-15; Exodus 1:22; Exodus 1:34; Numbers 3:45; Numbers 1:8; Numbers 1:18; Leviticus 12:2, Leviticus 1:12.
The first-born male of every clean animal was to be given up to the priest for sacrifice (Deuteronomy 12:6; Exodus 13:12; Exodus 1:34; Numbers 18:15-17).
But the first-born of unclean animals was either to be redeemed or sold and the price given to the priest (Leviticus 27:11-13, Leviticus 1:27). The first-born of an ass, if not redeemed, was to be put to death (Exodus 13:13; Exodus 1:34).