Alister McGrath discusses Martin Luther’s thoughts about the relationship between God’s word and the nature of the church.

Neither an episcopally ordained ministry, nor an institutional continuity with the apostolic church, are therefore necessary to safeguard the existence of the church, whereas the preaching of the gospel is essential to the identity of the church. ‘Where the word is, there is faith; and where faith is, there is the true church.’ The visible church is constituted by the preaching of the Word of God: no human assembly may claim to be the ‘church of God’ unless it is founded on this gospel. It is more important to the preach the same gospel as the apostles than to be a member of an institution which is historically derived from them (Christian Theology: An Introduction, 382).

 Hence, preaching was at the top of the to-do lists of the Reformers, e.g., in The Necessity of Reforming the Church, John Calvin said “no man is a true pastor of the Church who does not perform the office of teaching. . . . no man can claim for himself the office of bishop or pastor who does not feed his flock with the word of the Lord.”