The Prophet ﷺ said, "When one of you marries off his servant, whether his slave or his hired worker, he should not look at what is below the navel and above the knee."
عن النبي ﷺ قال: إذا زوج أحدكم خادمه- عبده، أو أجيره- فلا ينظر إلى ما دون السرة وفوق الركبة.
Abu Dawud narrated it (496, 4114) from Zuhayr bin Harb, who said, Waki narrated to us, Dawud bin Sawar Muzani narrated to me, from Amr bin Shuayb, from his father, from his grandfather, and he mentioned it. Its isnad is hasan because of Amr bin Shuayb.As for Dawud bin Sawar, Abu Dawud said, "The correct name is Sawar bin Dawud Muzani, Waki erred in it." I say, this is what Muhammad bin Abdul-Rahman Tufawi and Abdullah bin Bakr Sahmi said, among the teachers of Ahmad, as recorded in his Musnad (6756). This Sawar bin Dawud was deemed reliable by Ibn Main, and Ahmad said, "A Basran shaykh, there is no harm in him," and Ibn Hibban mentioned him among the trustworthy narrators. Moreover, he was corroborated, Uzai corroborated him.Abu Dawud narrated it (4113), and from him Bayhaqi (2/226), from Muhammad bin Abdullah bin Maymun, who said, Walid narrated to us, from Uzai, from Amr bin Shuayb, from his father, from his grandfather, that the Prophet ﷺ said, "If one of you marries his male slave, or his hired worker, to his female slave, let him not look at her private parts." Walid is Ibn Muslim, who conceals weaknesses in his chains of transmission, and here he narrated using the ambiguous word "from" rather than stating that he heard it directly, but Bayhaqi cited him using explicit wording of direct narration.Bayhaqi said, "This narration, when combined with the narration of Uzai, shows us that the intended meaning of the hadith is the prohibition of the master looking at her private parts when he marries her off, and that the private area of a female slave is what is between the navel and the knee."I say, this hadith is specific to the female slave, but the jurists made it general, saying that a woman's private area with respect to another woman is like a man's private area with respect to another man, that is, what is between the navel and the knee. So they said, therefore it is permissible for her to look at all of another woman's body except what is between these two parts, because of the shared nature between them and the general absence of desire, but this becomes forbidden when there is desire or fear of temptation.They also cited as evidence the hadith of Abu Ayub, who said, "I heard the Prophet ﷺ say, 'What is above the knees is part of the private area, and what is below the navel is part of the private area.'" Bayhaqi narrated it (2/229) and said, "It contains Saeed bin Abu Rashid Basri, who is daif."I say, this is an overgeneralization that contradicts the noble verse in which Allah, exalted is He, says, "And let them not display their adornment except what is apparent of it, and let them draw their veils over their bosoms, and not display their adornment except to their husbands, or their fathers, or their husbands' fathers, or their sons, or their husbands' sons, or their brothers, or their brothers' sons, or their sisters' sons, or their women, or those whom their right hands possess, or male attendants who have no desire, or children who have no knowledge of women's private aspects. And let them not stamp their feet so as to reveal what they conceal of their adornment. And turn to Allah in repentance, all of you believers, that you may succeed." [Nur 24:31]So Allah, exalted is He, excepted in this noble verse the places of adornment, which are generally the hand and forearm up to near the upper arm, the place of the bracelet, the head, the ears, and the neck, the place of the necklace, and the foot and part of the leg, the place of the anklet. And success comes from Allah.