Musnad Abu Ya'la al-Mawsili 54:10

Harun ibn Ma'ruf narrated to us, Abu 'Abd al-Rahman narrated to us, Sa'id narrated to us, Abu Marhum 'Abd al-Rahim ibn Maymun narrated to me, from Sahl ibn Mu'adh ibn Anas al-Juhani, from his father, from the Prophet, may Allah bless him and grant him peace: That he forbade the *habwah* (sitting with the knees drawn up to the chest while wrapped in a garment) on Friday while the Imam is delivering the sermon.