Exodus 15:23-25

New Revised Standard Version, Anglicised Catholic Edition

²³ When they came to Marah, they could not drink the water of Marah because it was bitter. That is why it was called Marah.^{[a] 24} And the people complained against Moses, saying, ‘What shall we drink?’ ²⁵ He cried out to the Lord; and the Lord showed him a piece of wood;^[b] he threw it into the water, and the water became sweet.

There the Lord^[c] made for them a statute and an ordinance and there he put them to the test.