Jericho in spite of all its ideal qualities then lacked the one thing essential. In spite of his exalted position, his wealth, his exploits, he lacked the one thing needful health. He was a leper and that nullified everything else. And they brought it to him. The appropriateness of this particular means for counteracting the effects of the curse is at once apparent.
Salt is the grand purifier and preserver.
It is by means of the salty vapors which the rays of the sun distill from the ocean that the atmosphere of our earth is kept healthy for its inhabitants. That is why the sea breezes act as such a tonic to the invalid and the convalescent. Salt prevents putrefaction. Though the men of Jericho were required to furnish the salt, and though the prophet now cast the same into the springs, yet he made it clear this would avail nothing unless the blessing of Jehovah accompanied the same. His power must operate if anything good was to be accomplished.