Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) was on the expedition of Tabuk. If they set out before the sun had declined, he would delay the Zuhr prayer until he combined it with Asr, and he would perform both together. And if they started the journey after the sun had declined, he would perform Asr along with Zuhr and then begin the journey. Similarly, if they set out before sunset, he would delay Maghrib until he performed it with Isha, and if they started the journey after sunset, he would hasten the Isha prayer and perform it together with Maghrib.