Ibn Jurayj (may Allah have mercy on him) narrates from Ata bin Abi Rabah (may Allah have mercy on him): "The Hajj is not missed, that is, it is not lost, until the dawn breaks after the night of Muzdalifah." He said: I said to Ata (may Allah have mercy on him): Did this reach you from the Prophet (peace and blessings be upon him)? He said: "Yes."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9816