Musnad Abu Ya'la al-Mawsili 143:2

Abu Bakr ibn Abi Shaybah narrated to us, Bishr ibn al-Mufaddal narrated to us, from Ghalib al-Qattan, from Bakr, from Anas, who said: We used to pray with the Messenger of Allah (may Allah bless him and grant him peace) in the intense heat. If one of us could not place his face firmly upon the ground, he would spread his garment and prostrate upon it.