What is the ruling when one cannot distinguish between pure and impure garments?

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If one cannot distinguish between pure and impure garments, performing conjecture (taharrī) is impermissible. The person must pray in each garment a number of times equal to the number of impure garments, thereby adding an extra prayer. This is the opinion attributed to Ibn al-Mājishūn. The obligation to perform the action with certainty is incumbent because it is possible to fulfill the obligation with certainty without hardship, similar to when pure water is indistinguishable from impure water, or when one forgets a specific prayer from a day. The distinction from impure utensils is that using an impure garment causes ritual impurity and invalidates the prayer immediately and ultimately, which is not the case here. Furthermore, praying in an impure garment is permissible if no other option exists, unlike impure water.