Exodus 15:24-26

Living Bible

²⁴ Then the people turned against Moses. “Must we die of thirst?” they demanded.

²⁵ Moses pleaded with the Lord to help them, and the Lord showed him a tree to throw into the water, and the water became sweet.

It was there at Marah that the Lord laid before them the following conditions, to test their commitment to him: ²⁶ “If you will listen to the voice of the Lord your God, and obey it, and do what is right, then I will not make you suffer the diseases I sent on the Egyptians, for I am the Lord who heals you.”