Exodus 24:4-5

LXX2012(i) 4 And Moses wrote all the words of the Lord; and Moses rose up early in the morning, and built an altar under the mountain, and [set up] twelve stones for the twelve tribes of Israel. 5 And he sent forth the young men of the children of Israel, and they offered whole burnt offerings, and they sacrificed young calves as a peace-offering to God.