Sunan Abi Dawud
Sunan Abi Dawud 4824
Regarding sitting in circles
Arabic hadith text
حَدَّثَنَا وَاصِلُ بْنُ عَبْدِ الأَعْلَى، عَنِ ابْنِ فُضَيْلٍ، عَنِ الأَعْمَشِ، بِهَذَا قَالَ كَأَنَّهُ يُحِبُّ الْجَمَاعَةَ
Translation
Al-A`mash said
It seems he liked collective gathering.