[Machine] I saw Hasan al-Basri on the day of Arafah after Asr prayer, sitting and making dua and remembrance of Allah. So the people gathered around him, and in another narration by Imam Muslim, I saw Hasan leaving the enclosure on the day of Arafah after Asr prayer, and he sat down and introduced himself.  

رَأَيْتُ الْحَسَنَ الْبَصْرِيَّ يَوْمَ عَرَفَةَ بَعْدَ الْعَصْرِ جَلَسَ فَدَعَا وَذَكَرَ اللهَ ﷻ فَاجْتَمَعَ النَّاسُ وَفِي رِوَايَةِ مُسْلِمٍ رَأَيْتُ الْحَسَنَ خَرَجَ يَوْمَ عَرَفَةَ مِنَ الْمَقْصُورَةِ بَعْدَ الْعَصْرِ فَقَعَدَ فَعَرَّفَ  

[Machine] Regarding the gathering of people on the day of Arafah in the mosques, they said, "It is an innovation. " And from Mansoor, from Ibrahim, he said, "It is an innovation." And from Qatadah, from Al-Hasan, he said, "The first one to do that was Ibn Abbas. "  

عَنِ اجْتِمَاعِ النَّاسِ يَوْمَ عَرَفَةَ فِي الْمَسَاجِدِ فَقَالَا هُوَ مُحْدَثٌ وَعَنْ مَنْصُورٍ عَنْ إِبْرَاهِيمَ قَالَ هُوَ مُحْدَثٌ وَعَنْ قَتَادَةَ عَنِ الْحَسَنِ قَالَ أَوَّلُ مَنْ صَنَعَ ذَلِكَ ابْنُ عَبَّاسٍ