Sayyiduna Ibn Umar (may Allah be pleased with them both) said: "I saw the Messenger of Allah (peace and blessings be upon him): whenever travelling in haste was pressing upon him on a journey, he would delay the Maghrib prayer until he combined it with the Isha prayer."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13072