Riyad as-Saliheen 1605
Ibn 'Umar (May Allah be pleased with them) reported:
The Prophet ﷺ said, "The expiation for beating or slapping a slave on the face for something he has not done is to set him free."
[Muslim].
وعن ابن عمر رضي الله عنهما أن النبي ﷺ قال:
"من ضرب غلامًا له حدًا لم يأتهِ، أو لطمه، فإن كفارته أن يعتقه" ((رواه مسلم)).
Classification
Sahih (Authentic)
References
Riyad as-Saliheen 1605
Riyad as-Saliheen Book of Prohibited actions, Hadith 95