Musnad Ahmad 25:844

Hassan narrated to us, Ya’qub—meaning al-Qummi—narrated to us, from Ja’far, from Sa’id ibn Jubayr, from Ibn Abbas, who said: Umar ibn al-Khattab came to the Messenger of Allah, peace and blessings of Allah be upon him, and said: "O Messenger of Allah, I am ruined." He said: "And what has ruined you?" He said: "I turned my saddle last night." He said: So he did not reply to him with anything. He said: Then Allah revealed to His Messenger this verse: {Your wives are a place of cultivation for you, so come to your place of cultivation however you wish} [Al-Baqarah: 223]. "Approach, and turn away, and fear the anus and the menstruation."