Exod 15:22-25

Bitter Water Made Sweet 22Then Moses ordered Israel to set out from the Red Sea, and they went into the wilderness of Shur. They went three days in the wilderness and found no water.23When they came to Marah, they could not drink the water of Marah because it was bitter. That is why it was called Marah.24And the people complained against Moses, saying, “What shall we drink?”25He cried out to the Lord; and the Lord showed him a piece of wood; he threw it into the water, and the water became sweet. There the Lord! made for them a statute and an ordinance and there he put them to the test.