Musannaf Ibn Abi Shayba 1:1678

Waki’ narrated to us, from al-A’mash, from Salamah ibn Kuhayl, from Ibn Abza, from his father, who said: ‘Ammar said to ‘Umar: "Do you not remember the day we were in such and such a place, and we became ritually impure (junub), and we did not find water, so we rolled in the dust? When we came to the Prophet, may Allah bless him and grant him peace, we mentioned that to him." He said: "This would have been sufficient for you." Then he struck with his hands one strike, then blew into them, then wiped his face and his palms with them.