Your wives are a tilth for you; so go to your tilth (have sexual relations with your wives in any manner as long as it is in the vagina and not in the anus) when or how you will... (V.2:223)

Whenever Ibn `Umar recited the Qur'an, he would not speak to anyone till he had finished his recitation. Once I held the Qur'an and he recited Surat-al-Baqara from his memory and then stopped at a certain Verse and said, "Do you know in what connection this Verse was revealed? " I replied, "No." He said, "It was revealed in such-and-such connection." Ibn `Umar then resumed his recitation. Nafi` added regarding the Verse:--"So go to your tilth when or how you will" Ibn `Umar said, "It means one should approach his wife in.."

Jews used to say: "If one has sexual intercourse with his wife from the back, then she will deliver a squint-eyed child." So this Verse was revealed:-- "Your wives are a tilth unto you; so go to your tilth when or how you will." (2.223)