Quoting from Richard A. Krause’s paper “Worship Wars at the Dawn of a New Millennium: Lutheranism and the Means of Grace vs. the 'Success Story' of American Evangelicalism":
The church must be visible. Its true marks, the right preaching of the Word and the administration of the sacraments, are to be perceptible to the eye of the people. Though the church does not consist in external things such as ceremonies and rites, and though her true essence remains unknown to the unbeliever, the presence of the church is established by the preaching of the gospel and the administration of the sacraments. Lutherans insist that the church is not upheld by the piety of the believers but by the external means of Word and sacrament. As Luther said, "Where the gospel is, there is Christ. Where Christ is, there is the Holy Spirit and his kingdom, the true kingdom of heaven."
The liturgy of the church is the word in action. It is properly referred to as Gottesdienst, or "divine service." The liturgy is God's leiturgia, his public service to his fallen creation through Jesus Christ in the Holy Spirit. The liturgy is comprised of the deeds and words of Jesus. They are cleansing words that bring forgiveness, life, and salvation. God is the subject, and we are the objects of his service. Unfortunately, in the English-speaking world, worship is most often understood primarily as something we do to recognize the greatness of God. Such a view stands in opposition to Lutheran worship. It turns worship into an anthropocentric activity defined by what we do and what we understand God to be. Lutheran worship will always emphasize the opposite idea, that worship comes from God to us. The gifts of God always stand at the center. Thus, worship is not just another program of the church, but it is the very heartbeat of our life with God as he comes with his gifts and we respond in our prayers, praise, and hymns.