Compare the marginal reference. Evil doers seem to draw down the wrath of God upon their heads, and so become, as it were, the scapegoats of the comparatively righteous.

The wicked shall be a ransom for the righteous - God often in his judgments cuts off the wicked, in order to prevent them from destroying the righteous. And in general, we find that the wicked fall into the traps and pits they have digged for the righteous.

The (h) wicked [shall be] a ransom for the righteous, and the transgressor for the upright.
(h) God will cause that to fall on their own heads, which they intended against the just by delivering the just, and putting the wicked in their places.

The wicked shall be a ransom for the righteous,.... Not to make satisfaction for them, as Christ is a ransom for his people; but as a ransom is in the room of another, so the wicked cometh in the stead of the righteous, and into the trouble he is delivered from; as Haman for Mordecai, which instance Jarchi mentions; see Proverbs 11:8; or when a body of people are threatened with divine vengeance; and this falls upon the wicked, whose sins caused it, and the righteous are delivered from it; as in the case of Achan, and the seven sons of Saul, Joshua 7:26. And sometimes God turns the wrath of the princes of the earth from his own people, and causes it to fall upon the wicked, and so they are a ransom for them; as Sennacherib intended the destruction of the Jews, but was called off in providence to fall upon the Egyptians, Ethiopians, and Sabeans, and therefore they are said to be a ransom for them; see Isaiah 43:3; and sometimes wicked men are the means of a ransom or deliverance of the righteous, as Cyrus was of the Jews: and it may be considered, as the word used signifies a "cover" (d), whether it will not bear this sense, that the wicked are a cover for the righteous, and oftentimes protect and defend them; so the earth helped the woman, Revelation 12:16;
and the transgressor for the upright; which are but different characters of the same persons, bad and good men; and the sense is the same as before.
(d)

The righteous is often delivered out of trouble, and the wicked comes in his stead, and so seems as a ransom for him.

(Compare Proverbs 11:8). By suffering what they had devised for the righteous, or brought on them, the wicked became their ransom, in the usual sense of substitutes (compare Joshua 7:26; Esther 7:9).

18 The godless becometh a ransom for the righteous;
And the faithless cometh into the place of the upright.
The thought is the same as at Proverbs 11:8. An example of this is, that the same world-commotion which brought the nations round Babylon for its destruction, put an end to Israel's exile: Cyrus, the instrument in God's hands for inflicting punishment on many heathen nations, was Israel's liberator, Isaiah 43:3. Another example is in the exchange of places by Haman and Mordecai, to which Rashi refers. כּפר is equivalent to λύτρον, ransom; but it properly signifies price of atonement, and generally, means of reconciliation, which covers or atones for the guilt of any one; the poll-tax and "oblations" also, Exodus 30:15., Numbers 31:50, are placed under this point of view, as blotting out guilt: if the righteousness of God obtains satisfaction, it makes its demand against the godless, and lets the righteous go free; or, as the substantival clause 18b expresses, the faithless steps into the place of the upright, for the wrath passes by the latter and falls upon the former. Regarding בּוגד, vid., Proverbs 2:22. Thus, in contrast to the ישׁר, he is designated, who keeps faith neither with God nor man, and with evil intention enters on deceitful ways - the faithless, the malicious, the assassin.

A ransom - The wicked shall be brought into those troubles, which were designed by wicked men for the righteous: thus Haman was a ransom for Mordecai.