Deuteronomy 25:12

Then thou shall cut off her hand,.... Which was to be done not by the man that strove with her husband, or by any bystander, but by the civil magistrate or his order. This severity was used to deter women from such an immodest as well as injurious action, who on such an occasion are very passionate and inconsiderate. Our Lord is thought to refer to this law, Matthew 5:30; though the Jewish writers interpret this not of actual cutting off the hand, but of paying a valuable consideration, a price put upon it; so Jarchi; and Aben Ezra compares it with the law of retaliation, "eye for eye", Exodus 21:24; which they commonly understand of paying a price for the both, c. lost and who adds, if she does not redeem her hand (i.e. by a price) it must be cut off:

thine eye shall not pity [her]; on account of the tenderness of her sex, or because of the plausible excuse that might be made for her action, being done hastily and in a passion, and out of affection to her husband; but these considerations were to have no place with the magistrate, who was to order the punishment inflicted, either in the strict literal sense, or by paying a sum of money.