When the heat grows intense, delay the prayer until it cools, for the severity of heat is from the blast of Hell.
إذا اشتد الحر فأبردوا عن الصلاة فإن شدة الحر من فيح جهنم
Its chain of transmission is sahih. Bukhari related it 1/142, in the book of prayer times, on delaying Dhuhr due to heat. Muslim related it 1/430, number 615, in the book of mosques, on the recommendation of delaying Dhuhr due to heat. Tirmidhi related it 4/711, number 2592, in the description of Hell, on what has been said about the fire having two breaths. Ibn Majah related it 2/1444, number 4319, in the book of asceticism, on the description of the fire. And Malik related it in Muwatta 1/15, in the book of prayer times, on the prohibition of praying in the intense midday heat.