2 Kings 2:19-22

Then the men of the city said to Elisha, “Behold now, the situation of this city is pleasant, as my lord sees; but the water is bad and the land is unfruitful.” He said, “Bring me a new jar, and put salt in it.” So they brought it to him. He went out to the spring of water and threw salt in it and said, “Thus says the LORD, ‘I have purified these waters; there shall not be from there death or unfruitfulness any longer.’ ” So the waters have been purified to this day, according to the word of Elisha which he spoke.