And that saving faith is a firm assent — based on the certain knowledge of divine revelation — ingenerated in our minds by the Holy Spirit through the word of the Gospel, an assent to everything that God has revealed to us in his Word, and especially the promises of life that were made in Christ; hereby each and every believer, relying with constant confidence in God, steadfastly determines that forgiveness of sins was promised not only to believers generally but also granted to him in particular, and that he himself has received eternal righteousness and from it, life, out of God’s mercy because of the merit of Jesus Christ alone.

Synopsis of a Purer Theology, Vol. 1, 353.

Along with Scripture itself we willingly grant that when one hears the Word of God it is “the power of God for those who are being saved” (1 Cor 1:18), that it “is the seed that has been sown in our hearts” (Luke 8:11), and that it “is a two-edged sword piercing the soul” (Heb 4:12). Nevertheless, we disagree with those who ascribe a power of the following sort to the outward preaching of the Gospel as it strikes the ears: that ingenerating faith is a property inherent in the preaching, as though the very performance of that action achieves it, and as though the operation of the Holy Spirit is bound up in it. Even though by God’s command the outward preaching is a necessary prerequisite of faith for adults, nevertheless the outward act of preaching is not sufficient for faith if it is not accompanied by the efficacy of the Holy Spirit as he reveals the meaning of the Gospel inwardly and as he presents and seals it upon the ‘ears’ of the heart. For “neither he who plants is anything, nor is he who waters, but he who grants the increase — God” (1 Cor 3:7). We must therefore see to it here that we not go head over heels to the extremes and pull apart what belongs together, or mix up what should be kept apart, but attributing to the instrument what belongs properly to the primary cause, and with the same sense. Nor should we do so by looking for the Spirit apart from the Word, or by looking for an understanding of the Word apart from the internal revelation of the Spirit; or, once the Word is understood, by looking for the assent and true confidence form the Word itself (or from the one who administers it) apart from the internal revelation by the Spirit, and to do so by the light of our understanding.

Synopsis of a Purer Theology, Vol. 1, 355-356.