Exodus 17:5–6

5 The Lord answered Moses, “Go on ahead of the people and take some of the elders of Israel with you. Take the staff you struck the Nile with in your hand and go. 6 I am going to stand there in front of you on the rock at Horeb; when you hit the rock, watere will come out of it and the people will drink.” Moses did this in the sight of the elders of Israel.