Proverbs 20:26

26 A wise king winnoweth the godless, And bringeth over them the wheel. A variant to Pro 20:8, but here with the following out of the figure of the winnowing. For אופן with מזרה is, without doubt, the wheel of the threshing-cart, עגלה, Isa 28:27.; and thus with מזרה, the winnowing fork, מזרה is to be thought of; vid., a description of them along with that of the winnowing shovel, רחת, in Wetzstein's Excursus to Isa., p. 707ff. We are not to think of the punishment of the wheel, which occurs only as a terrible custom of war (e.g., Amo 1:3). It is only meant that a wise king, by sharp and vigorous procedure, separates the godless, and immediately visits them with merited punishment, as he who works with the winnowing shovel gives the chaff to the wind. Most ancient interpreters think on אופן (from אפן, vertere) in its metaphorical meaning: τρόπος (thus also Lwenstein, he deals with them according to merit), or the wheel of fortune, with reference to the constellations; thus, misfortune (Immanuel, Meri). Arama, Oetinger, and others are, however, on the right track.

See here, 1. What is the business of magistrates. They are to be a terror to evil-doers. They must scatter the wicked, who are linked in confederacies to assist and embolden one another in doing mischief; and there is no doing this but by bringing the wheel over them, that is, putting the laws in execution against them, crushing their power and quashing their projects. Severity must sometimes be used to rid the country of those that are openly vicious and mischievous, debauched and debauching. 2. What is the qualification of magistrates, which is necessary in order to do this. They have need to be both pious and prudent, for it is the wise king, who is both religious and discreet, that is likely to effect the suppression of vice and reformation of manners.

20:26 A king represents God on earth, so he should support the godly and punish the wicked.