Exodus 15:23

and, when they came in towards Marah they could not drink the waters of Marah, for they were bitter, - for this taut, was the name thereof called Marah.

Numbers 33:8

And they brake up from before Hahiroth, and passed through the midst of the sea towards the desert, - and went their way a journey of three days in the desert of Etham, and encamped in Marah.

Ruth 1:20

And she said unto them, Do not call me Naomi, - call me Mara, for the Almighty hath dealt very bitterly with me:

Treasury of Scripture Knowledge

Summary

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.

Bible References

Marah

Numbers 33:8
And they brake up from before Hahiroth, and passed through the midst of the sea towards the desert, - and went their way a journey of three days in the desert of Etham, and encamped in Marah.
Ruth 1:20
And she said unto them, Do not call me Naomi, - call me Mara, for the Almighty hath dealt very bitterly with me: