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requiring a company of men to be exclusively devoted to this ministry, the primitive office of the first-born was superseded by that of the Levites ( Numbers 3:11-13 ), and it was ordained that the first-born of man and of unclean animals should henceforth be redeemed ( 18:15 ).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 ; 22:29 ; 34:20 ; Numbers 3:45 ; 8:17 ; 18:16 ; Leviticus 12:2 Leviticus 12:4 .

The first-born male of every clean animal was to be given up to the priest for sacrifice ( Deuteronomy 12:6 ; Exodus 13:12 ; 34:20 ; 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 27:27 ). The first-born of an ass, if not redeemed, was to be put to death ( Exodus 13:13 ; 34:20 ).

These dictionary topics are from
M.G. Easton M.A., D.D., Illustrated Bible Dictionary, Third Edition,
published by Thomas Nelson, 1897. Public Domain, copy freely.