Exodus 24:4-6

Amplified Bible

⁴ Moses wrote down all the words of the Lord. Then he got up early in the morning, and built an altar [for worship] at the foot of the mountain with twelve pillars (memorial stones) representing the twelve tribes of Israel. ⁵ Then he sent young Israelite men, and they offered burnt offerings and sacrificed young bulls as peace offerings to the Lord. ⁶ Moses took half of the blood and put it in large basins, and [the other] half of the blood he sprinkled on the altar.