Musnad Ahmad

Abdur Rahman bin Sabit says that once Hafsa bint Abdur Rahman was visiting me. I said to her, "I want to ask you a question, but I feel shy to ask." She said, "Nephew, do not be shy." I said, "What is the ruling about approaching women from the back?" She replied, "Umm Salamah told me that the men of the Ansar did not approach their women from the back, because the Jews used to say that whoever approaches his wife from behind, his offspring will be cross-eyed. When the Muhajirun came to Madinah, they also married Ansari women and would approach them from behind. But one woman refused to obey her husband in this matter and said, 'You cannot do this until I ask the Prophet (peace be upon him) about its ruling.' So that woman came to Umm Salamah and mentioned it to her. Umm Salamah said, 'Sit down, the Prophet (peace be upon him) will be here soon.' When the Prophet (peace be upon him) arrived, the woman felt shy to ask this question and left. Later, Umm Salamah informed the Prophet (peace be upon him) about this matter. The Prophet (peace be upon him) said, 'Call that Ansari woman!' So she was called, and the Prophet (peace be upon him) recited this verse before her: 'Your wives are your fields, so come to your field as you wish,' and said, 'In the front opening (whether the man comes from behind or from the front).'