We believe that God works through the means of grace, that is, through the Word and the sacraments of baptism, absolution, and the Lord’s Supper. In these ways, He creates and nourishes faith and bestows on repentant sinners the gifts of forgiveness, life, and salvation that Christ won for the whole world on the cross.
So that we may obtain [justifying faith in Christ], the ministry of teaching the Gospel and administering the Sacraments was instituted. Through the Word and Sacraments, as through instruments, the Holy Spirit is given. He works faith, when and where it pleases God, in those who hear the good news that God justifies those who believe that they are received into grace for Christ’s sake. This happens not through our own merits, but for Christ’s sake. … (Augsburg Confession: Article 5)
We will now return to the Gospel, which does not give us counsel and aid against sin in only one way. God is superabundantly generous in His grace: First through the spoken Word, by which the forgiveness of sins is preached in the whole world. This is the particular office of the Gospel. Second, through Baptism. Third, through the holy Sacrament of the Altar. Fourth, through the Power of the Keys. Also through the mutual conversation and consolation of brethren, “Where two or three are gathered” (Matthew 18:20) and other such verses. (Smalcald Articles: Part 3, Article 4)