2 Kings 2:21

And he—cast the salt in there, and said, &c.— The manner in which Elisha sweetened this fountain, and made the soil fruitful by casting salt into the water, was in order to make the miracle more conspicuous; for salt is a thing which of all others makes water less drinkable, and ground more barren. There is a fountain at this very day towards the west of Jericho, which rises about three quarters of a league above the town in the way to Jerusalem, and yielding a great deal of water very excellent in its kind, runs along and fructifies the plain. See Josephus Bell. Jud. book 5: cap. 4 and Exodus 23:25.