Hilal ibn Yasaf said, "We used to sell linen in the house of Suwayd ibn Muqarrin. A slavegirl came out and said something to one of the men and that man slapped her. Suwayd ibn Muqarrin asked him, 'Did you slap her face? We were seven and we only had a single servant. Then one of us slapped her and the Prophet, may Allah bless him and grant him peace, ordered him to set her free.'"
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا آدَمُ، قَالَ: حَدَّثَنَا شُعْبَةُ، قَالَ: حَدَّثَنَا حُصَيْنٌ قَالَ: سَمِعْتُ هِلاَلَ بْنَ يَسَافٍ يَقُولُ: كُنَّا نَبِيعُ الْبَزَّ فِي دَارِ سُوَيْدِ بْنِ مُقَرِّنٍ، فَخَرَجَتْ جَارِيَةٌ فَقَالَتْ لِرَجُلٍ شَيْئًا، فَلَطَمَهَا ذَلِكَ الرَّجُلُ، فَقَالَ لَهُ سُوَيْدُ بْنُ مُقَرِّنٍ: أَلَطَمْتَ وَجْهَهَا؟ لَقَدْ رَأَيْتُنِي سَابِعَ سَبْعَةٍ وَمَا لَنَا إِلاَّ خَادِمٌ، فَلَطَمَهَا بَعْضُنَا، فَأَمَرَهُ النَّبِيُّ صلى الله عليه وسلم أَنْ يُعْتِقُهَا.
sunnah.com