It is narrated from Hazrat Anas (may Allah be pleased with him) that if the Prophet (peace and blessings be upon him) set out on a journey before the sun had passed its zenith, he would delay the Zuhr prayer until the time of Asr, then dismount and combine both prayers. And if the time of zenith occurred before setting out on the journey, the Prophet (peace and blessings be upon him) would first perform the Zuhr prayer and then mount (his ride).