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 - JPS_ASV_Byz
Numbers 33:8
8 And they journeyed from Penehahiroth, and passed through the midst of the sea into the wilderness; and they 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 Marah; for the Almighty hath dealt very bitterly with me.