Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
suyuti:1937a –

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. (Using translation from Abū Dāʾūd 4114)   

السيوطي:١٩٣٧a –

"إِذَا زوَّج أحدُكم خادِمَهُ -عبدَهُ أو أجيرهُ- فلا ينظُر إلى ما دون السُّرَّة وفوقَ الرُّكْبَةِ".  

[د] أبو داود [ق] البيهقى في السنن عن عمرو بن شعيب، عن أبيه، عن جده

See similar narrations below:

Collected by Abū Dāwūd
abudawud:4114 – Zuhayr b. Ḥarb > Wakīʿ > Dāwud b. Sawwār al-Muzanī > ʿAmr b. Shuʿayb from his father from his grandfather

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.  

أبو داود:٤١١٤ – حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ حَدَّثَنَا وَكِيعٌ حَدَّثَنِي دَاوُدُ بْنُ سَوَّارٍ الْمُزَنِيُّ عَنْ عَمْرِو بْنِ شُعَيْبٍ عَنْ أَبِيهِ عَنْ جَدِّهِ

عَنِ النَّبِيِّ ﷺ 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