Muwatta Malik, Book 20, Hadith 178 (USC-MSA)

Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to say, "Someone who does not stand at Arafa on the night of Muzdalifa before the dawn breaks has missed the hajj, and someone who stands at Arafa on the night of Muzdalifa before the dawn breaks has caught the hajj."

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يَقُولُ مَنْ لَمْ يَقِفْ بِعَرَفَةَ مِنْ لَيْلَةِ الْمُزْدَلِفَةِ قَبْلَ أَنْ يَطْلُعَ الْفَجْرُ فَقَدْ فَاتَهُ الْحَجُّ وَمَنْ وَقَفَ بِعَرَفَةَ مِنْ لَيْلَةِ الْمُزْدَلِفَةِ مِنْ قَبْلِ أَنْ يَطْلُعَ الْفَجْرُ فَقَدْ أَدْرَكَ الْحَجَّ ‏.‏

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also referenced under: Book 20, Hadith 878 (In-Book)