Luther on the purpose of the church:
[T]hat nothing else should take place therein than that our dear Lord Himself should speak with us through His holy Word, and we again speak with Him through prayer and praise.
When we have heard God’s Word we should bring before God our common holy smoke or incense, i.e., that we should together call upon Him and pray to Him.
Therefore where God’s Word is not preached, ’tis better people should neither sing nor read, nor come together.
Therefore we should know that God hath so ordained that none should come to knowledge of Christ or acquire forgiveness through Him or receive the Holy Ghost without external public means, but hath put such treasure in the oral word or preaching office, and will not establish it in a corner or secretly in the heart, but will have it cried aloud and imparted openly among the people, as Christ enjoined: ‘Go ye into all the world and preach the Gospel to every creature.’