صَحِيحُ مُسْلِمٍ
Sahih Muslim 619 a
The Book of Mosques and Places of Prayer
It is recommended to pray Zuhr at the beginning of its time when there is no intense heat
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو الأَحْوَصِ، سَلاَّمُ بْنُ سُلَيْمٍ عَنْ أَبِي إِسْحَاقَ، عَنْ سَعِيدِ بْنِ وَهْبٍ، عَنْ خَبَّابٍ، قَالَ شَكَوْنَا إِلَى رَسُولِ اللَّهِ صلى الله عليه وسلم الصَّلاَةَ فِي الرَّمْضَاءِ فَلَمْ يُشْكِنَا .
Khabbab reported: We complained to the Messenger of Allah (ﷺ) (the difficulty of) saying prayer on the intensely heated (ground or sand), but he paid no heed to our complaint.
Sahih Muslim, 619 aSahihصحيح