Hastings' Dictionary of the Bible (1898)
FIRST'-BORN. The first-born male of every Jewish family and of all beasts was consecrated to God in commemoration of the judgment which God brought upon the first-born of Egypt. Ex 13:2. Several provisions of the Jewish law relate to the first-born. He received a double portion of the estate, Deut 21:17, and officiated as priest of the family in the father's absence or death. The privileges of the first-born were obviously great in the cases of Esau and Reuben, Gen 27:29, Gen 27:36; 1 Chr 5:1-2, but might be forfeited, as these two cases show.
The religious pre-eminence of the first-born ceased when the priesthood was committed exclusively to the tribe of Levi. Num 3:12-13. 50) should be paid for the redemption of all the first-born of succeeding generations; and this redemption-money became part of the sacred revenue. Num 8:17; Josh 18:16. The first-born of all beasts used in sacrifice were devoted to the Lord, Ex 13:2, but the first-born of unclean animals might be redeemed with the addition of one-fifth of the value, Lev 27:13; otherwise, they were sold, exchanged, or destroyed. Ex 13:13; Lev 27:27.
It is supposed that dogs were never redeemed, Deut 23:18. The titles "the first-born of every creature," Col 1:15, and "the first-begotten" of God, Heb 1:6, belong exclusively to Christ. The first of the two might be translated the "firstborn" or begotten (not created) "before every creature," and both expressions denote a dignity superior to men and angels and the whole creation.