Musnad Ahmad Hadith 26698

It is narrated from Umm Salamah (may Allah be pleased with her) 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 Muhajireen came to Madinah Munawwarah, they also married Ansari women and would approach them from behind, but one woman refused to obey her husband in this matter and said that until I ask the Prophet (ﷺ) about its ruling, you cannot do this. So that woman came to Umm Salamah and mentioned it to her. Umm Salamah said, "Sit down, the Prophet (ﷺ) will be here soon." When the Prophet (ﷺ) arrived, the woman felt shy to ask this question, so she left. Later, Umm Salamah informed the Prophet (ﷺ) about this matter, so the Prophet (ﷺ) said, "Call that Ansari woman!" So she was called, and the Prophet (ﷺ) recited this verse before her: "Your wives are your tilth, so come to your tilth as you wish," and said, "In the front opening (whether the man comes from behind or from the front)."