Rules about Performing Salah (Prayer) in an Unclean Cloth Regardless One Knows it or Not

9. Ali ibn Ibrahim has narrated from his father from ‘Abd Allah ibn al-Mughirah from ‘Abd Allah ibn Sinan who has said the following: “I once asked abu ‘Abd Allah عليه السلام, about a man who finds semen or blood in his clothes. He (the Imam) said, ‘If he learns before performing Salah (prayer) that there is semen in his clothes, then performs Salah (prayer) in it without washing; he is required to perform his Salah (prayer) again, but if he did not know, he is not required to perform his Salah (prayer) again. If he thinks that something has happened then investigates but does not see anything it is sufficient to pour water on it.’”