TT #629 · Parashas Ki Seitzei · Seventh Aliyah · Passuk 25:03
Forty times he shall strike him; he shall not add, lest he continue to strike him beyond these with a great blow, and your brother be degraded before your eyes.
Torah Temimah points to Makkot 23a.
TT lemma: לֹא יֹסִיף.
English: ‘He shall not add’ – they appoint as officers only those who are deficient in strength and abundant in understanding.
Derash on the prohibition against adding (Bavli) — the character of the officer is derived from the Torah’s concern not to exceed.
The person who administers the lashes must be weak enough that he cannot easily over-strike and wise enough to count accurately and stop when required.