Sahih al-Bukhari 1112
صحيح البخاري#1112Sahihحَدَّثَنَا 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.
Narrated Anas bin Malik:Whenever the Prophet (ﷺ) started on a journey before noon, he used to delay the Zuhr prayer 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)
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 18:32