The Scriptures clearly ascribe both repentance and faith wherever they exist to Divine influence.† Whence many have concluded that they cannot be duties required of sinners. If sinners have been required from the pulpit to repent or believe, they have thought it sufficient to show the absurdity of such exhortations by saying, A heart of flesh is of God’s giving: faith is “not of ourselves; it is the gift of God:” as though these things were inconsistent, and it were improper to exhort to any thing but what can be done of ourselves, and without the influence of the Holy Spirit.

The whole weight of this objection rests upon the supposition that we do not stand in need of the Holy Spirit to enable us to comply with our duty. If this principle were admitted, we must conclude either, with the Arminians and Socinians, that “faith and conversion, seeing they are acts of obedience, cannot be wrought of God;”* or, with the objector, that, seeing they are wrought of God, they cannot be acts of obedience. But if we need the influence of the Holy Spirit to enable us to do our duty, both these methods of reasoning fall to the ground.

And is it not manifest that the godly in all ages have considered themselves insufficient to perform those things to which nevertheless they acknowledge themselves to be obliged? The rule of duty is what God requires of us; but he requires those things which good men have always confessed themselves, on account of the sinfulness of their nature, insufficient to perform. He “desireth truth in the inward part:” yet an apostle acknowledges, “We are not sufficient of ourselves to think any thing as of ourselves: but our sufficiency is of God.”—“The Spirit,” saith he, “helpeth our infirmities; for we know not what we should pray for as we ought: but the Spirit itself maketh intercession for us with groanings which cannot be uttered.” The same things are required in one place which are promised in another: “Only fear the Lord, and serve him in truth with all your heart.”—“I will put my fear in their hearts that they shall not depart from me.” When the sacred writers speak of the Divine precepts, they neither disown them nor infer from them a self-sufficiency to conform to them, but turn them into prayer: “Thou hast commanded us to keep thy precepts diligently. Oh that my ways were directed to keep thy statutes!” In fine, the Scriptures uniformly teach us that all our sufficiency to do good or to abstain from evil is from above; repentance and faith, therefore, may be duties, notwithstanding their being the gifts of God.

If our insufficiency for this and every other good thing arose from a natural impotency, it would indeed excuse us from obligation; but if it arise from the sinful dispositions of our hearts, it is otherwise. Those whose eyes are “full of adultery, and (therefore) cannot cease from sin,” are under the same obligations to live a chaste and sober life as other men are: yet, if ever their dispositions be changed, it must be by an influence from without them; for it is not in them to relinquish their courses of their own accord. I do not mean to suggest that this species of evil prevails in all sinners; but sin in some form prevails and has its dominion over them, and to such a degree that nothing but the grace of God can effectually cure it. It is depravity only that renders the regenerating influence of the Holy Spirit necessary. “The bare and outward declaration of the word of God,” says a great writer,† “ought to have largely sufficed to make it to be believed, if our own blindness and stubbornness did not withstand it. But our mind hath such an inclination to vanity that it can never cleave fast to the truth of God, and such a dulness that it is always blind and cannot see the light thereof. Therefore there is nothing available done by the word without the enlightening of the Holy Spirit.”

Excerpt from: The Gospel Worthy of All Acceptation. Part III, Answers to Objections.

Fuller, A. G. (1988). The Complete Works of Andrew Fuller: Controversial Publications. (J. Belcher, Ed.) (Vol. 2, pp. 379–380). Harrisonburg, VA: Sprinkle Publications.