Exodus 15:22-25

Then Moses led Israel from the Red Sea, and they went into the Wilderness of Shur; they went [a distance of] three days (about thirty-three miles) in the wilderness and found no water. Then they came to Marah, but they could not drink its waters because they were bitter; therefore it was named Marah (bitter). The people [grew discontented and] grumbled at Moses, saying, “What are we going to drink?” Then he cried to the LORD [for help], and the LORD showed him a tree, [a branch of] which he threw into the waters, and the waters became sweet. T here the LORD made a statute and an ordinance for them, and there He tested them