Shaykh Muḥammad ibn Ṣāliḥ al-ʿUthaymīn [d. 1421 AH] said:

If confusion should occur in [an individual’s] clothing such that he lacks the ability to distinguish between that which is ḥarām for him to utilise [due to the presence of impurity] and that which is ḥalāl [for the purpose of covering himself during prayer], then this issue has two scenarios:

The first is that the prohibition is borne from the right of Allāh such as a silk garment [for a man]. A person possesses one synthetic silk garment and ten authentic ones and lacks the ability to distinguish between them. [According to the Ḥanbalī madh`hab] he should pray the same ṣalāh eleven times, [one with each garment] to be assured he prayed at least one ṣalāh in a ḥalāl garment.

The second scenario is that a piece of clothing is ḥarām in relation to the right of another individual. For example, a person possesses a piece of clothing that is stolen and another that he owns outright and he cannot distinguish between the two. [According to the Ḥanbalī madh`hab] he should pray the same ṣalāh a number of times that corresponds to the number of stolen garments in his possession plus one ṣalāh. If it is said: How can he pray in stolen clothing that belongs to another person? Is this not gaining benefit from another’s possession without express permission?

We reply: benefiting from another’s possession here is permissible due to extenuating circumstances. Additionally, reparation would be obligatory on this person towards the owner corresponding to the value of the stolen clothing. Thus, the right of the true owner is not disregarded. What is correct [in this issue] is that a person should inspect and examine the clothes he is confused regarding, and then pray in the garment that is most likely permissible according to his estimation. There is no blame on him for this as Allāh does not charge a soul except [with that within] its capacity. If the situation is such that there exists no clue as to which piece of clothing is permissible for him, then he should pray in whichever one he wills. This is because here he has no choice but to pray in a garment that is ḥarām on him and thus he does not need to repeat his ṣalāh [should he then possess a garment he knows is ḥalāl].

Endnotes:

Source: Al-Sharḥ al-Mumtiʿ 1:67
Translated by: Riyāḍ al-Kanadī