Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) said: We went out with the Prophet (peace and blessings be upon him) on the expedition of Tabuk, and he used to pray Zuhr and Asr together, and Maghrib and Isha together.
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17241