It was narrated that Anas bin Malik said:
"If the Messenger of Allah (ﷺ) was setting out on a journey before the sun passed its zenith, he would delay Zuhr until the time of 'Asr, then he would stop and combine the prayer. If the sun passed its zenith before he set out, he would pray Zuhr and then set off.
English reference: Vol. 1, Book 6, Hadith 587
Arabic reference: Book 6, Hadith 593