Leviticus 13:55-57

New Century Version

⁵⁵ After the piece with the mildew has been washed, the priest must look at it again. If the mildew still looks the same, the piece is unclean, even if the mildew has not spread. You must burn it in fire; it does not matter if the mildew is on one side or the other.

⁵⁶ “But when the priest looks at that piece of leather or cloth, the mildew might have faded after the piece has been washed. Then the priest must tear the mildew out of the piece of leather or cloth (either woven or knitted). ⁵⁷ But if the mildew comes back to that piece of leather or cloth (either woven or knitted), the mildew is spreading. And whatever has the mildew must be burned with fire.