Webster(i)
23 And when they came to Marah, they could not drink of 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 the LORD; and the LORD showed him a tree, which he cast into the waters, and the waters were made sweet: there he made for them a statute and an ordinance, and there he proved them,