1 Kings 18:31-32

31Elijah picked up 12 stones, one for each of the tribes that were Jacob's descendants. Jacob was the man that the Lord had given the new name ‘Israel’.

32Elijah used the 12 stones to build an altar that would give honour to the Lord. He dug a hole in the ground all around it. The hole was big enough to contain 15 litres of seeds.