Martin Chemnitz masterfully answers the question that so many have regarding the relationship of justifying faith and the means of grace, i.e. the Word and the Sacraments. First, he explains that faith lays hold of Christ’s merit, the grace of God, and the efficacy of the Spirit in the Word and the Sacraments. Christ and His merit is the object of faith, but faith apprehends Him in those divinely instituted means, so that one can rightly say that faith in the sacraments justifies.
He also speaks of the circumcision of Abraham and the baptism of Cornelius (Acts 10:1-2) and addresses the role of the sacraments in those who already have justifying faith. Many use these examples to say that the sacraments are superfluous to faith, that they are useless. But Chemnitz begs to differ:
For God does not confer and convey grace in this life just once, so that it is at once complete and perfect, so that as long as we are in this life God would will to convey and confer nothing more, and that a person would need to receive nothing more from God; but God is always giving and man is always receiving, in order that we may be joined more and more fully and perfectly to Christ, and may hold the forgiveness of sins or reconciliation more firmly, so that the benefits of redemption which have been begun in us may be preserved and strengthened and may grow and increase. (Examination of the Council of Trent, vol. 2, p. 76-77).