Exodus 15:23-25

Darby Translation

²³ And they came to Marah, and could not drink the waters of Marah, for they were bitter; therefore the name of it was called Marah.

²⁴ And the people murmured against Moses, saying, What shall we drink?

²⁵ And he cried to Jehovah; and Jehovah shewed him wood, and he cast it into the waters, and the waters became sweet. There he made for them a statute and an ordinance; and there he tested them.