Musnad Ahmad 28:200

Yahya narrated to us, from Ibn ‘Ajlan, ‘Amr ibn Shu‘ayb narrated to us, from his father, from his grandfather, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) forbade buying and selling in the mosque, and that poetry be recited in it, and that lost property be announced in it, and he forbade circles [of gathering] on Friday before the prayer."