Sahih Muslim
Sahih Muslim 615 d
The recommendation to delay Zuhr (until it has cooled down) in severe heat for one who finds it too hot in route to join the congregation
Arabic hadith text
وَحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا عَبْدُ الْعَزِيزِ، عَنِ الْعَلاَءِ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ "إِنَّ هَذَا الْحَرَّ مِنْ فَيْحِ جَهَنَّمَ فَأَبْرِدُوا بِالصَّلاَةِ "
Translation
Abu Huraira reported that the Messenger of Allah (ﷺ) said
This heat is from the exhalation of Hell-fire, so delay the prayer till it is cool.