Sahih al-Bukhari 536, 537Book 9, Hadith 14
حَدَّثَنَا عَلِيُّ بْنُ عَبْدِ اللَّهِ، قَالَ حَدَّثَنَا سُفْيَانُ، قَالَ حَفِظْنَاهُ مِنَ الزُّهْرِيِّ عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، عَنْ أَبِي هُرَيْرَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " إِذَا اشْتَدَّ الْحَرُّ فَأَبْرِدُوا بِالصَّلاَةِ، فَإِنَّ شِدَّةَ الْحَرِّ مِنْ فَيْحِ جَهَنَّمَ ". " وَاشْتَكَتِ النَّارُ إِلَى رَبِّهَا فَقَالَتْ يَا رَبِّ أَكَلَ بَعْضِي بَعْضًا. فَأَذِنَ لَهَا بِنَفَسَيْنِ نَفَسٍ فِي الشِّتَاءِ، وَنَفَسٍ فِي الصَّيْفِ، فَهُوَ أَشَدُّ مَا تَجِدُونَ مِنَ الْحَرِّ، وَأَشَدُّ مَا تَجِدُونَ مِنَ الزَّمْهَرِيرِ ".
The Prophet (ﷺ) said, "In very hot weather delay the Zuhr prayer till it becomes (a bit) cooler because the severity of heat is from the raging of the Hell-fire. The Hell-fire of Hell complained to its Lord saying: O Lord! My parts are eating (destroying) one another. So Allah allowed it to take two breaths, one in the winter and the other in the summer. The breath in the summer is at the time when you feel the severest heat and the breath in the winter is at the time when you feel the severest cold."