Then Moses led Israel on from the Red Sea, and they went out to the Wilderness of Shur. They journeyed for three days in the wilderness without finding water.
References for Exodus 15:22
They came to Marah, but they could not drink the water at Marah because it was bitter-that is why it was named Marah.
References for Exodus 15:23
The people grumbled to Moses, "What are we going to drink?"
So he cried out to the Lord, and the Lord showed him a tree. When he threw it into the water, the water became drinkable. He made a statute and ordinance for them at Marah and He tested them there.
He said, "If you will carefully obey the Lord your God, do what is right in His eyes, pay attention to His commands, and keep all His statutes, I will not inflict any illness on you I inflicted on the Egyptians. For I am the Lord who heals you."
Then they came to Elim, where there were 12 springs of water and 70 date palms, and they camped there by the waters.
References for Exodus 15:27