Narrated 'Amr b. Suh'aib:

On his father's authority, said that his grandfather reported the Prophet (ﷺ) said: When one of you marries his female servant to his slave or to his employee, he should not look at her private part below the navel and above the knees. Abu Dawud said: The correct name is Sawwad b. Dawud al-Muzani al-Sairafi (and not Dawud b. Sawwad as mentioned in the chain). The narrator waki' misunderstood it.

حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا وَكِيعٌ، حَدَّثَنِي دَاوُدُ بْنُ سَوَّارٍ الْمُزَنِيُّ، عَنْ عَمْرِو بْنِ شُعَيْبٍ، عَنْ أَبِيهِ، عَنْ جَدِّهِ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏

‏ إِذَا زَوَّجَ أَحَدُكُمْ خَادِمَهُ عَبْدَهُ أَوْ أَجِيرَهُ فَلاَ يَنْظُرْ إِلَى مَا دُونَ السُّرَّةِ وَفَوْقَ الرُّكْبَةِ ‏

‏ ‏.‏ قَالَ أَبُو دَاوُدَ صَوَابُهُ سَوَّارُ بْنُ دَاوُدَ الْمُزَنِيُّ الصَّيْرَفِيُّ وَهِمَ فِيهِ وَكِيعٌ ‏.‏