Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) said: The Jews used to say that a child becomes cross-eyed only when a man comes into the front passage from behind. So Allah Almighty revealed this verse: "Your wives are a tilth for you, so come to your tilth however you wish." [Surah al-Baqarah: 223], that is, he may come from the front or from behind, but only into the designated place.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14103