Sahih al-Bukhari 1111
صحيح البخاري#1111SahihNarrated Anas bin Malik:Whenever the Prophet (ﷺ) started the journey before noon, he used to delay the Zuhr prayer till the time for the `Asr prayer and then he would dismount and pray them together; and whenever the sun declined before he started the journey he used to offer the Zuhr prayer and then ride (for the 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: 18:31