It is narrated from Sulayman bin Yasar that Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) led the people in the morning prayer, then went to his land at al-Jurf and found traces of a wet dream on his clothes. Then he said: When we began eating rich (fatty) food, the veins softened.
Then he took a ritual bath, washed the traces of the wet dream from his clothes, and repeated the prayer.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 802