Daraqutni

Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) narrates: On the occasion of the Battle of Tabuk, it was the practice of the Noble Prophet (peace and blessings be upon him) (during the journey, at the time of setting out from a stop) that when the Noble Prophet (peace and blessings be upon him) set out before the sun had declined, he would delay the Zuhr prayer until the time of Asr, and then perform both prayers together at the time of Asr. And when he set out after the sun had declined, he would perform Zuhr and Asr prayers together, and then set out. Similarly, when he set out before Maghrib, the Noble Prophet (peace and blessings be upon him) would delay the Maghrib prayer until he performed it together with the Isha prayer. And when the Noble Prophet (peace and blessings be upon him) set out after the sun had set, then he would perform the Isha prayer early and combine it with Maghrib. Imam Abu Dawood has stated: This narration has only been transmitted by Qatadah.