Musnad Abu Ya'la al-Mawsili 209:76

Kamil narrated to us, Hammad bin Salamah narrated to us, from Asim, from Abu Salih, from Umm Salamah: That she saw a relative of hers blowing [on the ground] when he wanted to prostrate. She said: "Indeed, the Messenger of Allah (ﷺ) said to a boy who was called Rabah: 'Dust your face.'"