Musannaf Ibn Abi Shayba 3:2544

Waki’ narrated to us, he said: Mughira ibn Ziyad narrated to us, he said: I was in the Sacred Mosque (al-Masjid al-Haram), and I had a wet dream (ihtalamtu) multiple times in one night. So I asked ‘Ata’, and he said: "Sleep, even if you have a wet dream ten times."