Yoreh Deah Siman 267 Seif 31

לא הִכָּהוּ עַל יָדוֹ וּצְמָתָהּ וְסוֹפָהּ לַחֲזֹר, אֵינוֹ יוֹצֵא לְחֵרוּת.

Seif 31

If the master struck his hand and it became swollen, he doesn’t receive his freedom.