Exodus 15:23 WEB

²¹  Miriam answered them, 'Sing to Yahweh, for he has triumphed gloriously: The horse and his rider he has thrown into the sea.'

²²  Moses led Israel onward from the Red Sea, and they went out into the wilderness of Shur; and they went three days in the wilderness, and found no water.

²³  When they came to Marah, they couldn't drink from the waters of Marah, for they were bitter. Therefore the name of it was called Marah.{Marah means bitter.}

²⁴  The people murmured against Moses, saying, 'What shall we drink?'

²⁵  Then he cried to Yahweh. Yahweh shown him a tree, and he threw it into the waters, and the waters were made sweet. There he made a statute and an ordinance for them, and there he tested them;