Sayyiduna Usamah bin Zayd (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) returned from Arafah until, when he reached near the mountain pass, he dismounted and urinated, then performed ablution, but not thoroughly. I said to him (peace and blessings be upon him): The prayer! He (peace and blessings be upon him) said: "The prayer is ahead of you." Then he (peace and blessings be upon him) mounted, and when he came to Muzdalifah, he dismounted and performed ablution thoroughly. Then the iqamah was called and he (peace and blessings be upon him) led Maghrib. Then everyone made his camel kneel at his own place; then the iqamah for Isha was called, he (peace and blessings be upon him) led Isha, and did not pray anything between the two.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9500