אַרְבָּעִ֥ים יַכֶּ֖נּוּ לֹ֣א יֹסִ֑יף פֶּן־יֹסִ֨יף לְהַכֹּת֤וֹ עַל־אֵ֙לֶּה֙ מַכָּ֣ה רַבָּ֔ה וְנִקְלָ֥ה אָחִ֖יךָ לְעֵינֶֽיךָ׃ (ס)
사십까지는 때리려니와 그것을 넘기지는 못할지니 만일 그것을 넘겨 과다히 때리면 네가 네 형제로 천히 여김을 받게 할까 하노라
Rashi on Deuteronomy
לא יסיף HE SHALL NOT EXCEED — From here is derived the prohibition referring to one who strikes his fellow man (Sanhedrin 86b; cf. Ketubot 33a).
Sforno on Deuteronomy
מכה רבה, more than the victim’s general constitution can bear.