Matthew Poole and continuators on 2 Kings 2:21

21 And he went forth unto the spring of the waters, and cast the salt in there , and said, Thus saith the LORD, I have healed these waters, there shall not be from thence any more death , or barren land.

Which was in it self idle and ineffectual, considering both the quality of Salt, and the small quantity of it, and the place where it was put; the Fountain which quickly works out any thing which is put into it; See Levit. 11. 36. but was onely used as a sign of God's Presence and Power, which did the thing; compare Exod. 15. 25. 2 King. 4. 41. and 6. 6.

i. e. Hurt, or Danger, as death is oft used, (as 2 Cor. 11. 23.) to Men or Beasts, by drinking of it, as formerly.