God might, indeed, by his absolute power, prevent evil; but he will not wrong and despoil his own creature, man, whom he created righteous and holy. He acts with man in a manner that corresponds with the nature with which he has endowed him. Hence he proposes laws to which he attaches rewards and punishments—he commands us to embrace the good and shun the evil; and that we may do this, he both grants his grace, without which we can do nothing, and also encourages our diligence and labor. But if a man come short of doing what he ought, his sin and negligence are chargeable upon himself, and not upon God, although God had the power to prevent it, and yet did not.

God hardens some men's hearts, as he did Pharaoh's, and he wills to harden them, or he hardens them according to his decreeing will; "Whom he will he hardens", (Romans 9:18) this he does not by any positive act, by infusing hardness and blindness into the hearts of men; which is contrary to his purity and holiness, and would make him the author of sin; but by leaving men to their natural blindness and hardness of heart; for the understanding is naturally darkened; and there is a natural blindness, hardness, and callousness of heart, through the corruption of nature, and which is increased by habits of sinning.

First, the offering of occasions which can be procured only by the peculiar providence of God by the concourse of circumstances and the proposition of objects, fitted to move faculties constituted in this or that way (in which manner God does not infuse wickedness into the minds of men, but draws out into action the wickedness latent there).

God doth not infuse the lust, or excite it, though he doth present the object about which the lust is exercised. God delivered up Christ to the Jews, he presented him to them, but never commanded them to crucify him, nor infused that malice into them, nor quickened it; but he, seeing such a frame, withdrew his restraining grace, and left them to the conduct of their own vitiated wills. … God created the grape, and filled the vine with a sprightliness, but he doth never infuse a drunken frame into a man, or excite it. … In short, though it be by God's permission that we can do evil, yet it is not by his inspiration that we will to do evil; that is wholly from ourselves.

Thus God is said to harden men, not by positive hardening, or working anything in the creature, but by not working, not softening, leaving a man to the hardness of his own heart, whereby it is unavoidable, by the depravation of man’s nature, and the fury of his passions, but that he should be further hardened. … If you put fire near to wax or resin, both will melt; but when the fire is removed, they return to their natural quality of hardness and brittleness. The positive act of the fire is to melt and soften, and the softness of the rosin is to be ascribed to that, but the hardness is from the resin itself, wherein the fire hath no influence, but only a negative act by a removal of it; so when God hardens a man, he only leaves him to that stony heart which he derived from Adam, and brought with him into the world.