Musnad Ahmad 1101:19

Yahya narrated to us, from Wa'il ibn Dawud, who said: I heard Abdullah al-Bahiy [saying] that a group of riders stopped by Uthman ibn Affan and praised him and lauded him. Al-Miqdad ibn al-Aswad was there, so he took a handful of earth and threw it into the faces of the riders. He said: The Prophet of Allah, peace and blessings of Allah be upon him, said: "If you hear the praisers, throw dust into their faces."