The Prophet ﷺ said, "The intensity of the heat is from the breath of Hell, so cool the prayer by delaying it."
حدثنا هشيم عن هشام عن ابن سيرين
عن النبي ﷺ قال شدة الحر من فيح جهنم فأبردوا بالصلاة
Its isnad is sahih. Hisham is Ibn Hassan Azdi Qurdusi, one of the great scholars, a reliable and firm hadith master. Bukhari mentioned him in al-Kabir 4/2, 197-198, and Dhahabi in Tadhkirat al-Huffaz 1:154. Ibn Sirin is Muhammad. The hadith was narrated by the whole group, with similar wording, as in al-Muntaqa, 534.