In Heidelberg Catechism Q/A 65 we confess:
65. Since, then, we are made partakers of Christ and all His benefits by faith only, where does this faith come from?
The Holy Spirit works faith in our hearts1 by the preaching of the Holy Gospel,2 and confirms it by the use of the holy sacraments.3
1 Jn 3:5; Rom 10:17; 1 Cor 2:10-14; Eph 2:8; Php 1:29; 2 Rom 10:17; 1 Pt 1:23-25; 3 Mt 28:19-20; Rom 4:11; 1 Cor 10:16
In the words of Reformed church planter Rev. Danny Hyde in his helpful book, Welcome to a Reformed Church (I believe this book can be downloaded for free as an “ePub” for those more tech savvy than me; just “google” it):
By the means of the preached Word and the sacraments of baptism and the Lord’s Supper, our gracious God meets with us in public worship. By these means, God the Father stoops down to our level as little children in order to communicate to us as well as to bring us into intimate fellowship with Himself. Although these means are not outwardly flashy, exciting, or even seemingly powerful to accomplish what we say they do, they are God’s chosen means to sustain His weary pilgrims in the wilderness and to strengthen their faith.
The best of the Reformed tradition has believed in the centrality of the means of grace in the life of the church. When we try and be wiser than God in replacing this missional thrust of Christ’s church with home groups, programs and social justice, we have no guarantee of God’s ongoing blessing. Indeed, there is a place for private means of grace like solitary meditation and prayer, family worship and group Bible study, but these are secondary in the life of the Christian. They flow out of and depend upon the public means of grace administered by an ordained minister.