Sahih al-Bukhari 1112
صحيح البخاري#1112SahihNarrated 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
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 18:32