Imam al-Sha'bi (may Allah have mercy on him) narrates from Sayyiduna Urwah al-Ta'i (may Allah be pleased with him), who said: I came to the Messenger of Allah (peace and blessings be upon him) while he (peace and blessings be upon him) was at the standing place of Muzdalifah, and I said: "O Messenger of Allah! I have come from the two mountains of Tayyi'. I have worn myself out and exhausted my mount. By Allah! On every mountain I came down at, I stood there. So has my Hajj been accomplished, O Messenger of Allah?" The Messenger of Allah (peace and blessings be upon him) said: "Whoever prays this prayer with us, having already come to Arafah by night or by day, he has removed his grime (completed his rites) and his Hajj is complete."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14462