Genesis 25:31

31Jacob answered, “First sell me your 25:31 In later times, this was the right of the firstborn to take over as head of the family and to receive a double share of the inheritance (cf Deut 21:17). The rewards given to Jacob appear to have been even greater (Gen 27:37). Furthermore, in Jewish tradition it was reported that before the tabernacle was set up, sacrifices were offered by the firstborn of a family.birthright (the rights of a firstborn).”