It is narrated from Yahya bin Abdur Rahman bin Hatib that he performed Umrah with several camel riders along with Sayyiduna Umar bin Khattab (may Allah be pleased with him), among whom was also Sayyiduna Amr bin As (may Allah be pleased with him). Sayyiduna Umar bin Khattab (may Allah be pleased with him) dismounted near water at night, and Sayyiduna Umar (may Allah be pleased with him) had a wet dream, and morning was near, and there was no water in the caravan. So Sayyiduna Umar (may Allah be pleased with him) rode until he came to the water, and began to wash his clothes until it became light. Sayyiduna Amr bin As (may Allah be pleased with him) said to Sayyiduna Umar (may Allah be pleased with him): Morning has come, we have clothes, leave your garment, it will be washed, and wear one of our garments. So Sayyiduna Umar (may Allah be pleased with him) said: Strange, O Amr bin As! If you have clothes, do you think all people will have clothes? By Allah! If I do this, it will become a Sunnah. Rather, I wash where impurity is known, and I sprinkle water where it is not known.

Imam Malik, may Allah have mercy on him, said that if a person finds a trace of a wet dream on his clothes and does not know when the wet dream occurred, nor does he remember seeing anything in his dream, then he should perform ghusl (ritual bath) from the last dream he remembers. If he performed any prayers after that dream, he should repeat them, because sometimes a person experiences a wet dream but does not see anything, and sometimes he sees something but there is no wet dream. So when he sees wetness, ghusl becomes obligatory for him. The reason for this is that Sayyiduna Umar bin Khattab, may Allah be pleased with him, repeated only the prayer after his last sleep, and did not repeat the prayers before that.