Rev. Klaus Detlev Schulz writes, Mission is thus the activity by which God puts His salvific intentions into practice. That is, God intentionally uses His Word and Sacraments as signs and testimonies of His will toward man, ‘intended to awaken and confirm faith in those who use them.’ [AC XIII 1) Thus God does not forego these means but uses them to bring about His work of salvation.
We affirm that mission is a kerygmatic activity of the Church. For God effects faith through the Gospel, not beyond or apart from it (Rom 10:14). Here again, scholars often question whether God can and will also save those who have not yet encountered Christ through the means of grace … Lutheran theology insists on the normal arrangements by which God calls believers to faith, and it dismisses circumstances outside of such normal arrangements. To suggest otherwise would mean that God would contradict Himself and would undermine and destroy the assurance and promise He has given with His Word.
From: Mission from the Cross: The Lutheran Theology of Mission by Klaus Detlev Schulz, St. Louis: Concordia Publishing House, 2009:153-154.