Parashas Beshalach · EXTRA (side-ring) · Passuk 15:23
Sefaria — Or HaChaim on Beshalach 15:23
English: ויבאו מרתה , They arrived at Marah, etc. Why is this place sometimes referred to as Marah and other times as Maratah? Apparently the original name of the oasis was Maratah and the spring it contained did not have a separate name. The Torah added: "they could not drink the waters of Marah," meaning that the spring itself was now named Marah because its waters were bitter. The name Marah therefore also became the name of the oasis after the Israelites had camped there and G'd had shown Moshe how to make the waters of that spring palatable. The words כי מרים הם were an allusion to an experience the Israelites were going to have.
Commentary (Rishon) on a TT-silent passuk — EXTRA side-ring only.
See the Or HaChaim on this passuk for the full derash and implications.