Mu‘ādh ibn Anas al-Juhani (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) forbade Hibwah (a sitting position) on Friday while the Imām is delivering the sermon.
This Hadīth is abrogated as Abu Dawūd pointed out. The meaning of it is as related by Mu‘ādh ibn Anas from the Prophet (may Allah's peace and blessings be upon him) who forbade Hibwah on Friday while the Imām is delivering the sermon. Hibwah means sitting with the thighs drawn up to the belly and the calves to the thighs, held together by the arms, a belt, a turban, etc. This was forbidden by the Prophet (may Allah's peace and blessings be upon him) when the Imām is delivering the Friday sermon, for two reasons: 1. Hibwah might cause one to fall asleep and sleep through the sermon. 2. The ‘Awrah might become exposed, because most of the [ancient] Arabs only wore one piece of clothing, so sitting in this way might expose their ‘Awrah. An-Nawawi (may Allah have mercy upon him) comments: “Hibwah was a common practice among Arabs in their gatherings. If sitting this way uncovers a part of one's ‘Awrah, it is forbidden.” However, if there is no such a risk, then Hibwah is fine, because the prohibition was for a specific reason and if that reason that no longer exists, the prohibition is removed. We also know from a Hadīth that ‘Abbād ibn Tamīm reported from his uncle who said “I saw the Messenger of Allah (may Allah’s peace and blessings be upon him) lying on his back in the mosque with one of his legs over the other."