Sayyiduna Urwah bin Mudarris (may Allah be pleased with him) said: I came to the Messenger of Allah (peace and blessings be upon him) at Muzdalifah and said: "O Messenger of Allah! I have come from the two mountains of Tayyi'. I have not left a single mountain without standing on it. So is my Hajj valid?" He (peace and blessings be upon him) said: "Whoever prays this prayer with us, having departed from Arafah by night or by day, his Hajj is complete and he has fulfilled his rites (of removing his dishevelment)."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14466