Sahih al-Bukhari 4528
Sahih al-Bukhari · Book 65: Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)) · "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)
Narrated Jabir:
حَدَّثَنَا أَبُو نُعَيْمٍ ، حَدَّثَنَا سُفْيَانُ ، عَنِ ابْنِ الْمُنْكَدِرِ ، سَمِعْتُ جَابِرًا ـ رضى الله عنه ـ قَالَ كَانَتِ الْيَهُودُ تَقُولُ إِذَا جَامَعَهَا مِنْ وَرَائِهَا جَاءَ الْوَلَدُ أَحْوَلَ. فَنَزَلَتْ {نِسَاؤُكُمْ حَرْثٌ لَكُمْ فَأْتُوا حَرْثَكُمْ أَنَّى شِئْتُمْ}
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)