Deuteronomy 25:3 - Joseph Benson’s Commentary on the Old and New Testaments

Forty stripes he may give him The law of Moses very wisely limited the number of stripes, lest severe judges should order delinquents to be lashed to death, as was often done among the Romans, than which, perhaps, a more cruel kind of death can hardly be devised. And it seems not to have been superstition, but prudent caution, in the Jews, when they would not exceed thirty-nine stripes, lest, through mistake or forgetfulness, they should go beyond the bounds which they were commanded to keep. Thy brother should seem vile Lest the judges, by exceeding the bounds of humanity, and that compassion which was due to a brother, a partaker of human nature in common with themselves, and one of the same nation and community, civil and religious, should be accustomed to think despicably of their poor brethren, and set their lives at naught. Or lest he should be made contemptible to his brethren, either by this cruel usage of him, as if he were a brute beast; or by some deformity or infirmity of body, which excessive beating might produce.