It is narrated from Sayyiduna Mus'ab bin Sa'd bin Abi Waqqas (may Allah be pleased with him) that I used to carry the Book of Allah and Sayyiduna Sa'd bin Abi Waqqas (may Allah be pleased with him) would recite it. One day I scratched myself, so Sayyiduna Sa'd (may Allah be pleased with him) said: Perhaps you touched your private part. I said: Yes! So Sayyiduna Sa'd (may Allah be pleased with him) said: Get up and perform ablution. So I stood up, performed ablution, and then returned.