Cross reference
Exodus 15:23
23 And when they came to Marah, the water was no good for drinking, for the waters of Marah were bitter, which is why it was named Marah.
Numbers 33:8
8 And journeying on from before Hahiroth, they went through the sea into the waste land: they went three days' journey through the waste land of Etham and put up their tents in Marah.
Ruth 1:20
20 And she said to them, Do not let my name be Naomi, but Mara, for the Ruler of all has given me a bitter fate.