It is narrated from Hazrat Safwan Zahri (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: "Perform the prayer at a cooler time, for the severity of heat is due to the effect of the heat of Hell."
Hadith Referenceمسند احمد / أول مسند الكوفيين / 18306
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد حسن