Though revenge may be contrary to meekness, yet not but that a magistrate may revenge the quarrels of others. Indeed, it is not revenge in him, but doing justice. The magistrate is God’s lieutenant on earth. God has put the sword in his hand, and he is not ‘to bear the sword in vain’. He must be ‘for punishment of evil-doers’ (1 Pet. 2:14). Though a private person must not render to any man ‘evil for evil’ (Rom. 12:17), yet a magistrate may; the evil of punishment for the evil of offense. This rendering of evil is good. Private men must ‘put their sword in their sheath’, but the magistrate sins if he does not draw it out. As his sword must not surfeit through cruelty, so neither must it rust through partiality. Too much lenity in a magistrate is not meekness, but injustice. For him to indulge offenses, and say with a gentle reproof as Eli, ‘Why do you such things? Nay, my sons, for it is no good report that I hear’ (1 Sam. 2:23-24), this is but to shave the head that deserves to be cut off. Such a magistrate makes himself guilty.
-Thomas Watson, The Beatitudes, 109.