Mu'adh ibn Jabal · The Book on Traveling

"While the Prophet as at the Battle of Tabuk, if he wanted to depart before the sun's decline he would delay Zuhr so that he could pray it together with Asr. If he wanted to depart after the sun's decline, he would hasten Asr to Zuhr, and pray Zuhr and Asr together, and then move it. If he wanted to depart before Maghrib he would delay Maghrib until he prayed it with Isha, and if he wanted to depart after…

'Mu'adh bin Jabal would pray Al-Maghrib with the Messenger of Allah, then he would return to his people to lead them (in prayer)."

the Messenger of Allah said: "When one of you comes to the Salat and (finds) the Imam is in a position, then do as the Imam is doing."