It is narrated from Anas bin Malik (may Allah be pleased with him) that he said: When we prayed Zuhr behind the Messenger of Allah (peace and blessings be upon him), we would prostrate on our clothes to protect ourselves from the intensity of the heat.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2070