The Prophet used to pray Zuhr when the sun had passed its zenith.  

أَنَّ النَّبِيَّ ﷺ كَانَ يُصَلِّي الظُّهْرَ إِذَا دَحَضَتِ الشَّمْسُ  

"The Prophet used to pray the Hajir prayer, which you call 'Zuhr', when the sun had passed its zenith."  

كَانَ النَّبِيُّ ﷺ يُصَلِّي صَلاَةَ الْهَجِيرِ الَّتِي تَدْعُونَهَا الظُّهْرَ إِذَا دَحَضَتِ الشَّمْسُ  

"We complained to the Messenger of Allah about the heat of the sunbaked ground, but he did not respond to our complaint." (Sahih)Another chain with similar wording.  

شَكَوْنَا إِلَى رَسُولِ اللَّهِ ﷺ حَرَّ الرَّمْضَاءِ فَلَمْ يُشْكِنَا قَالَ الْقَطَّانُ حَدَّثَنَا أَبُو حَاتِمٍ حَدَّثَنَا الأَنْصَارِيُّ حَدَّثَنَا عَوْفٌ نَحْوَهُ  

"We complained to the Messenger of Allah about the heat of the sunbaked ground, but he did not respond to our complaint."  

شَكَوْنَا إِلَى النَّبِيِّ ﷺ حَرَّ الرَّمْضَاءِ فَلَمْ يُشْكِنَا