He must burn up the clothing, or the woven or knitted material of wool or linen, or any leather article that has the contamination in it, because the mildew is destructive; the article must be burned up.1
References for Leviticus 13:52
"But if, when the priest examines it, the mildew has not spread in the clothing, or the woven or knitted material, or the leather article,
he shall order that the contaminated article be washed. Then he is to isolate it for another seven days.
After the affected article has been washed, the priest is to examine it, and if the mildew has not changed its appearance, even though it has not spread, it is unclean. Burn it with fire, whether the mildew has affected one side or the other.
If, when the priest examines it, the mildew has faded after the article has been washed, he is to tear the contaminated part out of the clothing, or the leather, or the woven or knitted material.
But if it reappears in the clothing, or in the woven or knitted material, or in the leather article, it is spreading, and whatever has the mildew must be burned with fire.