Romans 9:18-20

Verse 18

Therefore hath he mercy on whom he will - This is the apostle's conclusion from the facts already laid down: that God, according to his own will and wisdom, in perfect righteousness, bestows mercy; that is to say, his blessings upon one part of mankind, (the Jews of old, and the Gentiles of the present time), while he suffers another part (the Egyptians of old, and the Jews of the present day) to go on in the abuse of his goodness and forbearance, hardening themselves in sin, till he brings upon them a most just and exemplary punishment, unless this be prevented by their deep repentance and general return to God through Jesus the promised, the real Messiah.
Verse 19

Why doth he yet find fault? - The apostle here introduces the Jew making an objection similar to that in Rom 3:7 : If the truth of God hath more abounded through my lie unto his glory, that is, if God's faithfulness is glorified by my wickedness, why yet am I also judged as a sinner? Why am I condemned for that which brings so much glory to him? The question here is: If God's glory be so highly promoted and manifested by our obstinacy, and he suffers us to proceed in our hardness and infidelity, why does he find fault with us, or punish us for that which is according to his good pleasure?
Verse 20

Nay but, O man, who art thou - As if he had said: Weak, ignorant man, darest thou retort on the infinitely good and righteous God? Reflect on thyself; and tell me, after thou hast abused the grace of God, and transgressed his laws, wilt thou cavil at his dispensations? God hath made, created, formed the Jewish nation; and shall the thing formed, when it hath corrupted itself, pretend to correct the wise and gracious Author of its being, and say, Why hast thou made me thus? Why hast thou constituted me in this manner? Thou hast done me wrong in giving me my being under such and such conditions.

Old John Goodwin's note on this passage is at least curious: "I scarce (says he) know any passage of the Scripture more frequently abused than this. When men, in the great questions of predestination and reprobation, bring forth any text of Scripture which they conceive makes for their notion, though the sense which they put upon it be ever so uncouth and dissonant from the true meaning of the Holy Ghost, yet, if any man contradict, they frequently fall upon him with - Nay but, O man; who art thou? As if St. Paul had left them his heirs and successors in the infallibility of his spirit! But when men shall call a solid answer to their groundless conceits about the meaning of the Scriptures, a replying against God, it savours more of the spirit who was seen falling like lightning from heaven, than of His, who saw him in this his fall."
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