Musannaf Ibn Abi Shaybah 38864 — A man in ihram who wears trousers

It is narrated from Hafs bin Ubaydullah bin Anas: We used to travel with Sayyiduna Anas (may Allah be pleased with him) towards Makkah. When the sun passed its zenith while he was staying at a halting place, he would not mount until he had offered the Zuhr prayer. And when he mounted in the afternoon and the time of Asr was present, he would pray Asr. But if he had set out from his halting place before the sun passed its zenith and the time of prayer came, and we said: "The prayer?" he would say: "Keep going," until, when it was midway between the two prayers, he would dismount and combine Zuhr and Asr. Then he would say: "I saw the Prophet (peace and blessings be upon him), when he travelled continuously from morning until evening, do just this."