2 Kings 5:15 (KJV)

And his servants came near, and spake unto him, and said, My father, if the prophet had bid thee do some great thing, wouldest thou not have done it? how much rather then, when he saith to thee, Wash, and be clean?

Then went he down, and dipped himself seven times in Jordan, according to the saying of the man of God: and his flesh came again like unto the flesh of a little child, and he was clean.

And he returned to the man of God, he and all his company, and came, and stood before him: and he said, Behold, now I know that there is no God in all the earth, but in Israel: now therefore, I pray thee, take a blessing of thy servant.

But he said, As the Lord liveth, before whom I stand, I will receive none. And he urged him to take it; but he refused.

And Naaman said, Shall there not then, I pray thee, be given to thy servant two mules’ burden of earth? for thy servant will henceforth offer neither burnt offering nor sacrifice unto other gods, but unto the Lord.