Ibn Abbas said: Ibn Umar—may Allah forgive him—was mistaken. This clan of the Ansar, who were idolaters, lived alongside this clan of the Jews, who were People of the Book, and they used to consider them to have superiority over them in knowledge, so they followed much of their practice. Among the ways of the People of the Book was that they did not approach women except from one side (i.e. lying on the back), and that was the most concealing way for a woman to be. This clan of the Ansar had adopted this practice from them, while this clan of the Quraysh used to uncover their women completely and enjoy them coming, going, and lying on their backs.
When the Muhajirun came to Medina, a man from them married a woman from the Ansar and went to do that with her, but she rejected it and said to him, "We were only approached from one side, so do that or keep away from me." The matter spread between them, so it reached the Messenger of Allah, peace and blessings be upon him, and Allah, the Exalted and Glorious, revealed:
"Your wives are a tilth for you, so come to your tilth as you will,"meaning coming, going, and lying on her back, intending by that the place of the child.