Ubaydullah bin Abdullah bin Umar (may Allah have mercy on him) narrates from his father (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) combined Maghrib and Isha at Muzdalifah, with no prayer between them. He prayed three rak'ahs for Maghrib and two rak'ahs for Isha. Abdullah (may Allah be pleased with them both) used to pray at Muzdalifah in the same way until he met Allah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5441