"If the Messenger of Allah ﷺ was setting out on a journey before the sun passed its zenith, he would delay Zuhr until the time of 'Asr, then he would stop and combine the prayer. If the sun passed its zenith before he set out, he would pray Zuhr and then set off. (Using translation from Nasāʾī 586)
كَانَ رَسُولُ اللهِ ﷺ إِذَا ارْتَحَلَ قَبْلَ أَنْ تَزِيغَ الشَّمْسُ أَخَّرَ الظُّهْرَ إِلَى وَقْتِ الْعَصْرِ ثُمَّ يَنْزِلُ فَيَجْمَعُ بَيْنَهُمَا وَإِذَا زَاغَتِ الشَّمْسُ قَبْلَ أَنْ يَرْتَحِلَ صَلَّى الظُّهْرَ ثُمَّ رَكِبَ