Easton's Bible Dictionary: M. G. Easton, M.A., D.D.

First-born, Sanctification of the

A peculiar sanctity was attached to the first-born both of man and of cattle. God claimed that the first-born males of man and of animals should be consecrated to him, the one as a priest (Ex. 19:22, 24), representing the family to which he belonged, and the other to be offered up in sacrifice (Gen. 4:4).

Original from The Bible Foundation - bf.org. They claim public domain status for their original text.