Musannaf Ibn Abi Shayba 3:5879

Yazid ibn Harun narrated to us, from Hisham, from al-Hasan and Muhammad, they both said: We do not know of any Sunnah regarding combining two prayers while at home or while traveling, except between the Dhuhr and the Asr at Arafat, and between the Maghrib and the Isha at Jam' (Muzdalifah).