Exodus 15:22-25

Moses led Israel from the Red Sea on to the Wilderness of Shur. They traveled for three days through the wilderness without finding any water. They got to Marah, but they couldn’t drink the water at Marah; it was bitter. That’s why they called the place Marah (Bitter). And the people complained to Moses, “So what are we supposed to drink?” So Moses cried out in prayer to GOD. GOD pointed him to a stick of wood. Moses threw it into the water and the water turned sweet.