Sahih al-Bukhari 340

Sulayman ibn Harb narrated to us: Shu‘bah narrated to us, from al-Hakam, from Dharr, from Ibn Abd al-Rahman ibn Abza, from his father, who was present with Umar. Ammar said to him: ‘We were on a military expedition and became sexually impure.’ He said: ‘He blew on his hands.’