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.
Exodus 15:23 Cross References - UKJV
Numbers 33:8
8 And they departed from before Pihahiroth, and passed through the midst of the sea into the wilderness, and went three days' journey in the wilderness of Etham, and pitched in Marah.
Ruth 1:20
20 And she said unto them, Call me not Naomi, call me Mara: for the Almighty has dealt very bitterly with me.