John Gill Commentary 2 Kings 5:10

"And Elisha sent a messenger unto him, saying, Go and wash in the Jordan seven times, and thy flesh shall come again to thee, and thou shalt be clean." — 2 Kings 5:10 (ASV)

And Elisha sent a messenger unto him
Or returned an answer by Naaman's messenger; he did not go out to him, choosing to be retired, as he commonly did; and being perhaps employed in prayer for the cure; and it may be also to show his contempt of or little regard he had to worldly grandeur and honour, as well as to mortify the pride of Naaman:

saying, go and wash in Jordan seven times ;
so, according to the law of the cleansing the leper, he was to be sprinkled seven times, and on the seventh day his flesh was to be bathed or dipped all over in water, which is meant by washing here, (Leviticus 14:7Leviticus 14:9)

and your flesh shall come again to you ;
which was eaten and consumed by the disease on him:

and you shall be clean ;
freed from this pollution, or filthy disease, with which he was defiled; for a leper was reckoned unclean, (Leviticus 13:3) .