Exodus 24:4-8

4And Moses wrote down all the words of the Lord. He rose early in the morning and built an altar at the foot of the mountain, and twelve pillars, according to the twelve tribes of Israel.

5And he sent young men of the people of Israel, who offered burnt offerings and sacrificed peace offerings of oxen to the Lord.

6And Moses took half of the blood and put it in basins, and half of the blood he threw against the altar.

7Then he took the Book of the Covenant and read it in the hearing of the people. And they said, "All that the Lord has spoken we will do, and we will be obedient."

8And Moses took the blood and threw it on the people and said, "Behold the blood of the covenant that the Lord has made with you in accordance with all these words."