First, what he had to say on regeneration as a result of baptism (emphasis added):
But some say all are regenerate when they are baptized. Well, if you think so, stick to your own thoughts; I cannot help it. Simon Magus was certainly one exception; he was baptized on a profession of his faith; but so far from being regenerated by his baptism, we find Paul saying, "I perceive that thou art in the gall of bitterness, and in the bond of iniquity." And yet he was one of those regenerates, because he had been baptized. Ah! that doctrine only needs to be stated to sensible men, and they will at once reject it. Gentlemen that are fond of a filigree religion, and like ornament and show; gentlemen of the high Beau Brummel school will very likely prefer this religion, because they have cultivated their taste at the expense of their brain, and have forgotten that what is consistent with the sound judgment of a man can not be consistent with the Word of God. So much for the first point.
Second, to those who wish to give man credit in his choosing his regeneration with his so-called free will, he has a couple of paragraphs on that as well (again, emphasis added):
Neither is a man regenerated, we say, in the next place, by his own exertions. A man may reform himself very much, and that is well and good; let all do that. A man may cast away many vices, forsake many lusts in which he indulged, and conquer evil habits; but no man in the world can make himself to be born in God; though he should struggle never so much, he could never accomplish what is beyond his power. And, mark you, if he could make himself to be born again still he would not enter heaven, because there is another point in the condition which he would have violated—"unless a man be born of the Spirit, he can not see the kingdom of God." So that the best exertions of the flesh do not reach this high point, the being born again of the Spirit of God. And now we must say, that regeneration consists in this. God the Holy Spirit, in a supernatural manner—mark, by the word supernatural I mean just what it strictly means; supernatural, more than natural—works upon the hearts of men, and they by the operations of the divine Spirit become regenerate men; but without the Spirit they never can be regenerated. And unless God the Holy Spirit, who "worketh in us to will and to do," should operate upon the will and the conscience, regeneration is an absolute impossibility, and therefore so is salvation. "What!" says one, "do you mean to say that God absolutely interposes in the salvation of every man to make him regenerate?" I do indeed; in the salvation of every person there is an actual putting forth of the divine power, whereby the dead sinner is quickened, the unwilling sinner is made willing, the desperately hard sinner has his conscience made tender; and he who rejected God and despised Christ, is brought to cast himself down at the feet of Jesus. This is called fanatical doctrine, mayhap; that we can not help; it is scriptural doctrine, that is enough for us. "Except a man be born of the Spirit he can not see the kingdom of God; that which is born of the flesh is flesh, and that which is born of the Spirit is spirit." If you like it not, quarrel with my Master, not with me; I do but simply declare his own revelation, that there must be in your heart something more than you can ever work there. There must be a divine operation; call it a miraculous operation, if you please; it is in some sense so. There must be a divine interposition, a divine working, a divine influence, or else, do what you may, without that you perish, and are undone; "for except a man be born again, be can not see the kingdom of God." The change is radical; it gives us new natures, makes us love what we hated and hate what we loved, sets us in a new road; makes our habits different, our thoughts different, makes us different in private, and different in public. So that being in Christ it is fulfilled: "If any man be in Christ he is a new creature; old things are passed away, behold all things are become new."