Is it permissible to pray in a garment upon which the blood of another person has fallen due to an injury?

The prayer of whoever prays with impure blood on their garment or body, whether from themselves or others, is not valid. A small amount of it is excused according to the majority of scholars, but they differed on the definition of a "small amount." Some said it is the size of a dirham or less, others said it is determined by common custom, some said it is that which is not considered excessive by the heart, or that which people find acceptable.