Exodus 24:3-5

3Moses came and told the people all the commands of the Lord and all the ordinances. Then all the people responded with a single voice, “We will do everything that the Lord has commanded.”

4And Moses wrote down all the words of the Lord. He rose early the next morning and set up an altar and twelve pillars for the twelve tribes of Israel at the base of the mountain.

5Then he sent out young Israelite men, and they offered burnt offerings and sacrificed bulls as fellowship offerings to the Lord.