Bible: Deut. 21:15-17
Laws Concerning Children
21:15 Suppose a man has two wives, one whom he loves more than the other, 1 and they both 2 bear him sons, with the firstborn being the child of the less loved wife. 21:16 In the day he divides his inheritance 3 he must not appoint as firstborn the son of the favorite wife in place of the other 4 wife’s son who is actually the firstborn. 21:17 Rather, he must acknowledge the son of the less loved 5 wife as firstborn and give him the double portion 6 of all he has, for that son is the beginning of his father’s procreative power 7 – to him should go the right of the firstborn.