Sahih Bukhari Volume 1, Book 10, Hadith 629

حَدَّثَنَا مُسْلِمُ بْنُ إِبْرَاهِيمَ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنِ الْمُهَاجِرِ أَبِي الْحَسَنِ، عَنْ زَيْدِ بْنِ وَهْبٍ، عَنْ أَبِي ذَرٍّ، قَالَ كُنَّا مَعَ النَّبِيِّ صلى الله عليه وسلم فِي سَفَرٍ فَأَرَادَ الْمُؤَذِّنُ أَنْ يُؤَذِّنَ فَقَالَ لَهُ ‏"‏ أَبْرِدْ ‏"‏‏.‏ ثُمَّ أَرَادَ أَنْ يُؤَذِّنَ فَقَالَ لَهُ ‏"‏ أَبْرِدْ ‏"‏‏.‏ ثُمَّ أَرَادَ أَنْ يُؤَذِّنَ‏.‏ فَقَالَ لَهُ ‏"‏ أَبْرِدْ ‏"‏‏.‏ حَتَّى سَاوَى الظِّلُّ التُّلُولَ فَقَالَ النَّبِيُّ صلى الله عليه وسلم ‏{‏إِنَّ شِدَّةَ الْحَرِّ مِنْ فَيْحِ جَهَنَّمَ‏}‏

Narrated By Abu Dhar : We were in the company of the Prophet on a journey and the Mu'adhdhin wanted to pronounce the Adhan for the (Zuhr) prayer. The Prophet said to him, "Let it become cooler." Then he again wanted to pronounce the Adhan but the Prophet; said to him, "Let it become cooler." The Mu'adh-dhin again wanted to pronounce the Adhan for the prayer but the Prophet said, "Let it become cooler," till the shadows of the hillocks become equal to their sizes. The Prophet added, "The severity of the heat is from the raging of Hell."