Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) narrates: I used to pray Zuhr with the Messenger of Allah (peace and blessings be upon him), and because of the intense heat I would take a handful of pebbles so that they would cool in my palm, and then, when prostrating, I would place them under my forehead (to protect myself from the heat of the ground). This hadith is sahih (authentic) on the condition of Imam Muslim, but the two Shaykhs (Bukhari and Muslim) did not record it.