Abu Awanah said: I saw Hasan al-Basri (may Allah have mercy on him) on the day of Arafah after Asr; he supplicated to Allah and made remembrance, and the people gathered around him.
And in the narration of Muslim (bin Ibrahim) it says: I saw al-Hasan come out of the maqsurah (the screened-off enclosure) on the day of Arafah after Asr; then he sat down and observed (the gathering of) Arafah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9476