The Jews to keep within the letter of the law fixed 39 stripes as the maximum (compare the marginal reference.). Forty signifies the full measure of judgment (compare Genesis 7:12; Numbers 14:33-34); but the son of Israel was not to be lashed like a slave at the mercy of another. The judge was always to be present to see that the Law in this particular was not overpassed.
Related Commentaries of Deuteronomy 25:3
Deuteronomy 25:3
3 Forty stripes he may give him, and not exceed: lest, if he should exceed, and beat him above these with many stripes, then thy brother should seem vile unto thee.