From Sahih Bukhari (Hadith 1110):
Narrated Anas bin Malik:Whenever the Prophet (ﷺ) started a journey before noon, he used to delay the Zuhr prayer till the time of `Asr and then offer them together; and if the sun declined (at noon) he used to offer the Zuhr prayer and then ride (for the journey)
Reference: Bukhari 1110