Divorce (Kitab Al-Talaq)
Dawud :: Book 12 : Hadith 2214
Narrated Ikrimah:
A man made his wife like the back of his mother. He then had intercourse with her before he atoned for it. He came to the Prophet (peace_be_upon_him) and informed him of this matter. He asked (him): What moved you to the action you have committed? He replied: I saw the whiteness of her shins in moon light. He said: Keep away from her until you expiate for your deed.