The reading and hearing of the Holy Bible.
Romans 10:17 Faith comes by hearing, and hearing by the Word of God.
Romans 10:9 That if you confess with your mouth the Lord Jesus and believe in your heart that God has raised Him from the dead, you will be saved.
Revelation 2:29 He who has an ear, let him hear what the Spirit says to the churches.
1 Corithians 1:3 Grace to you and peace from God our Father and the Lord Jesus Christ.