Musannaf Ibn Abi Shayba 3:5529

Abu Khalid al-Ahmar narrated to us, from Ibn ‘Ajlan, from ‘Amr ibn Shu’ayb, from his father, from his grandfather, who said: The Messenger of Allah (may Allah bless him and grant him peace) forbade buying and selling in the mosque, and [he forbade] the public announcement of lost property.