Refuted: That believers must do good works to answer the demands of the law, as a covenant of works, if they will obtain salvation.
Truly our good works will never be able to answer these demands; and if we pretend to do them for that end, as the covenant of works will never accept them, so we cast dishonour on Christ, who has answered all these demands already for believers, by his perfect and perpetual obedience.
When God set Adam to seek salvation by his works, he was able for works; it was a thousand times easier to him to give perfect obedience, than for us to give sincere obedience. So we may be sure God bringing in a second covenant for the help of lost sinners, would never put them again on seeking salvation by works, after their strength for them was gone.
A View of the Covenant of Works by Thomas Boston
What comes first?
"But withal, it is to be remembered, that the true way to deal with a hard heart, to bring it to this temper [i.e. repentance], is to believe the gospel. As ravenous fowls first fly upward, and then come down on their prey; so must we 'first soar aloft in believing, and then we shall come down, in deep humiliation, sincere and free confession, and true repentance, Zech. xii. 10. " They shall look upon me whom they have pierced, and shall mourn. "Therefore the Scripture proposeth the object of faith, in the promise of grace, as a motive to repentance, that by a believing application thereof, the hard heart may be moved and turned, Joel ii. 13. "Turn unto the Lord your God, for he is gracious." One may otherwise toil long with it: but all in vain. "Without faith it is impossible to please God," Ileb. xi. 6. and therefore, impossible to reach true humiliation, right confession, and sincere repentance, which are very pleasing to him, Jer. xxxi. 18, 19, 20. The unbelieving sinner may be brought to roar under law horror; but one will never be a kindly mourner, but under gospel influences. When guilt stares one in the face, unbelief locks up the heart, as a keen frost doth the waters; but faith in the Redeemer's blood, melts it, to flow in tears of godly sorrow. Hard thoughts of God, which unbelief suggests to a soul stung with guilt, alienate that soul more and more from him; they render it like the worm, which, when one offers to tread upon it, presently contracts itself, and puts itself in the best posture of defense that it can: but the believing of the proclaimed pardon, touches the heart of the rebel so, that he casts down himself at the feet of his Sovereign, willingly yielding himself to return to his duty."
Thomas Boston, A View of the Covenant of Grace.