Imran bin Hdyr عمران بن حدير · The Book of the Times (of Prayer)

"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.