Marah in Fausset's Bible Dictionary

("bitterness".) A fountain in the desert of Shur, between the Red Sea and Sinai; Israel reached Marah three days after crossing to the Arabian side (Exodus 15:23; Numbers 33:8). Now Ain Huwarah, 47 miles from Ayun Muss, near the place of crossing the Red Sea. The beneficial effect of the tree cast into the bitter water by God's direction is probably the cause why now this fountain is less bitter than others in the neighborhood. The fountain rises from a large mound, a whitish petrifaction, deposited by the water, which seldom flows now; but there are traces of a formerly running stream. The Arabic Huwara means "destruction", analogous to the Hebrew "bitter". The cross is spiritually the tree which, when cast into life's bitterest waters, sweetens and heals them (Philemon 3:8; Acts 20:24; Acts 16:23-25; Acts 5:41; Romans 5:3).