Narrated Ibn 'Abbas:
"'Umar came to the Messenger of Allah (ﷺ) and said: 'O Messenger of Allah! I am ruined!' He said: 'Why are you ruined?' He said: 'I turned my mount during the night (meaning that he went into his wife from behind).'" He said: "So the Messenger of Allah (ﷺ) did not say anything in reply to him. Then Allah revealed this Ayah to the Messenger of Allah (ﷺ): 'Your wives are a tilth for you, so go to your tilth when or how you will (2:223).' From the front, the back, avoiding the anus, and menstruation." (ES)
English reference (ES): Vol. 5, Book 44, Hadith 2980 (ES)
Arabic reference (ES): Book 47, Hadith 3247 (ES)