صَحِيحُ مُسْلِمٍ
Sahih Muslim 615 d
The Book of Mosques and Places of Prayer
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
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 .
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.
Sahih Muslim, 615 dSahihصحيح