"I saw the Messenger of Allah when people came to him and asked him about Hajj. The Messenger of Allah said: 'Hajj is Arafat. Whoever catches up with the night of Arafat before dawn comes on the night of Jam (Al-Muzdalifah), his Hajj is complete.'" (Using translation from Nasāʾī 3016)
شَهِدْتُ رَسُولَ اللهِ ﷺ بِعَرَفَةَ وَأَتَاهُ نَاسٌ مِنْ أَهْلِ نَجْدٍ فَسَأَلُوهُ عَنِ الْحَجِّ فَقَالَ رَسُولُ اللهِ ﷺ «الْحَجُّ عَرَفَةُ فَمَنْ أَدْرَكَ لَيْلَةَ عَرَفَةَ قَبْلَ طُلُوعِ الْفَجْرِ مِنْ لَيْلَةِ جَمْعٍ فَقَدْ تَمَّ حَجَّهُ»