(171) بَابُ قُبْلَةِ الرَّجُلِ الْجَارِيَةَ الصَّغِيرَةَ
Al-Hasan said, "If you avoid looking at the hair of anyone in yourfamily except your wife or a little girl, then do so."
Reference: Al-Adab Al-Mufrad 366
In-book reference: Book 19, Hadith 5
English translation: Book 19, Hadith 366