Nafi' reports: On one occasion, Abdullah bin Umar (may Allah be pleased with them both) led his companions in prayer. Afterwards, he remembered that he had touched his private part (which invalidated his ablution), so Abdullah bin Umar (may Allah be pleased with them both) performed ablution again (and repeated the prayer), but he did not instruct those people to repeat their prayer. Ibn Mahdi reports: I asked Sufyan, "Are you aware of any narrator who has also reported that those people repeated the prayer?" He replied, "No, only a narrator named Hammad has reported this."