Musnad Abu Ya'la al-Mawsili 109:25

Ishaq narrated to us, Sufyan narrated to us, from Muhammad ibn al-Munkadir, who heard Jabir saying: The Jews used to say: "Whoever approaches his wife in her front part from her back, the child will be cross-eyed." Then was revealed: "Your wives are a place of cultivation for you, so come to your place of cultivation however you wish."