Institutes of the Christian Religion by John Calvin.
Book 2: Of the knowledge of God the Redeemer, in Christ, as first manifested to the fathers, under the law, and thereafter to us under the gospel.
Chapter 3: “Everything Proceeding From The Corrupt Nature of Man Damnable.”
Section 12: Some people say that Paul in 1 Cor 15:10 states the he was a co-operator in grace. This is absurd as he does not say that the grace of God labored with him, but he pushes the whole merit of the labor to grace alone. He states clearly that in the labor which he provided, he did so more than all the other apostles, and that his labor (which was more than the others) was inspired, engineered, and acted through him and completed by the grace of God alone. He was nothing but an instrument in the hands of his master.
Section 13: Turning to Augustine to defend this point as there are Pelagians in any age who will refuse to accept it, Calvin refers to the second chapter of Treatise De Correptione et Gratis addressed to Valentinus where Augustine explains at length that Adam had the power to preserve in goodness but not the will to use that power. Quoting Calvin, “The grace offered by the Lord is not merely one which every individual has full liberty of choosing to receive or reject, but a grace which produces in the heart both choice and will: so that all the good works which follow after are its fruit and effect; the only will which yields obedience being the will which grace itself has made. In another place, Augustine uses these words, “Every good work in us is performed only by grace,” (August. Ep. 105).”
Section 14: Man is not drawn by an outward compulsion to trust in Christ, but is inwardly led so as to obey from the heart. Declaring that grace is given specifically and without measure to the elect, Augustine writes to Boniface, “We know that Divine grace is not given to all men, and that to those to whom it is given, it is not given either according to the merit of works, or according to the merit of the will, but by free grace: in regard to those to whom it is not given, we know that the not giving of it is a just judgment from God,” (August. ad Bonifac. Ep. 106) He later argues strongly that grace is not given to human merit as a reward for not rejecting the first grace. Pressing Pelagius to confess that unmeasured grace is necessary for us to complete any action, and since it is true grace, works are made of no effect. Quoting Calvin, “The matter cannot be more briefly summed up than in the eighth chapter of [Augustine’s] Treatise De Correptione et Gratia, where he shows, First, that human will does not by liberty obtain grace, but by grace obtains liberty. Secondly, that by means of the same grace, the heart being impressed with a feeling of delight, is trained to persevere, and strengthened with invincible fortitude. Thirdly, that while grace governs the will, it never falls; but when grace abandons it, it falls forthwith. Fourthly, that by the free mercy of God, the will is turned to good, and when turned, perseveres. Fifthly, that the direction of the will to good, and its constancy after being so directed, depend entirely on the will of God, and not on any human merit.” Thus the “free will” which is left to man is one which can neither be turned to God, nor continue in God except by grace, and that will derives all of its ability to do good at all from grace.