The decree which is the cause of the futurition of sin is nevertheless neither its physical cause (by the infusion of evil) nor its ethical cause (by the approbation of it). So although sin necessarily follows the decree, it cannot be said to flow from the decree. The decree does not flow into the thing, nor is it effective of evil, but only permissive and directive.

Yes, there is even in ourselves sin and corruption enough, so that there is no need that God should infuse into us either a new or greater measure of wickedness. Therefore, when God is said in the Scripture to harden (Ex. 7:13), to blind (John 12:40) and to deliver us up into a reprobate sense (Rom. 1:28), it is to be understood that God does it by just judgment, as a just judge and avenger.

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.

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).