1 Kings 18:30-32

30Then Elijah said to all the people, “Come near me.” So all the people approached him. Then he repaired the Lord’s altar that had been torn down:

31Elijah took twelve stones — according to the number of the tribes of the sons of Jacob, to whom the word of the Lord had come, saying, “Israel will be your name”  —

32and he built an altar with the stones in the name of the Lord. Then he made a trench around the altar large enough to hold about four gallons.