Exodus 15 places Marah immediately after the song celebrating Israel's deliverance at the sea. Moses led Israel into the wilderness of Shur, where the people traveled for three days without finding water.
When they reached Marah, they could not drink its bitter water and complained to Moses. Moses cried to the Lord, who showed him a piece of wood that he cast into the water, making it suitable to drink.
The narrative describes the event as a place of testing and connects it with God's call for Israel to listen diligently and obey His commandments.
Numbers 33 includes Marah in the itinerary of Israel's wilderness journey, placing it between the crossing of the sea and the encampment at Elim.