Deuteronomy 21:16
Then it shall be, when he maketh his sons to inherit that which he hath, that he may not make the son of the beloved firstborn before the son of the hated, which is indeed the firstborn:
More from Deuteronomy 21
If one be found slain in the land which the LORD thy God giveth thee to possess it, lying in the field, and it be not known who hath slain
Then thy elders and thy judges shall come forth, and they shall measure unto the cities which are round about him that is slain:
And it shall be, that the city which is next unto the slain man, even the elders of that city shall take an heifer, which hath not been wrought with, and which hath not drawn in the yoke;
And the elders of that city shall bring down the heifer unto a rough valley, which is neither eared nor sown, and shall strike off the heifer's neck there in the valley:
And the priests the sons of Levi shall come near; for them the LORD thy God hath chosen to minister unto him, and to bless in the name of the LORD; and by their word shall every controversy and every stroke