Must outer garments be washed if there is a doubt about impurity transferring to them from inner garments?

If you doubt that your outer garments have been defiled by impurity, according to the Malikis, you must perform nadḥ, which is sprinkling the garment with a small amount of water. Whoever omits nadḥ must repeat the prayers he performed in that garment if he was able to perform nadḥ and did not forget. Nadḥ is not obligatory according to the Hanbalis.