We were with the Prophet (ﷺ) on a journey and the Mu'adhdhin [call-maker for the (prayer)] wanted to pronounce the Adhân (call) for the Zuhr prayer. The Prophet (ﷺ) said, "Let it become cooler." He again (after a while) wanted to pronounce the Adhân but the Prophet (ﷺ) said to him, "Let it become cooler till we see the shadows of hillocks." The Prophet (ﷺ) added, "The severity of heat is from the raging of the Hell-fire, and in very hot weather, pray (Zuhr) when it becomes cooler." [1:514-O.B.]