Sahih al-Bukhari 1112
Sahih al-Bukhari · Book 18: Shortening the Prayers (At-Taqseer) · Whenever a person travels after midday, he should offer the Zuhr prayers and the ride for the journey
Narrated Anas bin Malik:
حَدَّثَنَا قُتَيْبَةُ ، قَالَ حَدَّثَنَا الْمُفَضَّلُ بْنُ فَضَالَةَ ، عَنْ عُقَيْلٍ ، عَنِ ابْنِ شِهَابٍ ، عَنْ أَنَسِ بْنِ مَالِكٍ ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا ارْتَحَلَ قَبْلَ أَنْ تَزِيغَ الشَّمْسُ أَخَّرَ الظُّهْرَ إِلَى وَقْتِ الْعَصْرِ، ثُمَّ نَزَلَ فَجَمَعَ بَيْنَهُمَا، فَإِنْ زَاغَتِ الشَّمْسُ قَبْلَ أَنْ يَرْتَحِلَ صَلَّى الظُّهْرَ ثُمَّ رَكِبَ.
Whenever the Prophet (ﷺ) started on a journey before noon, he used to delay the Zuhr prayers till the time for the 'Asr prayer and then he would dismount and offer them together; and whenever the sun declined before he started on a journey he used to offer the Zuhr prayers and then ride (for journey).