We need to know that Christ’s work of driving out the devil never ceases but continues to go on in the Christian world until the Last Day. Wherever Christ’s kingdom is, his wondrous work continues, causing the dumb to speak, the blind to see, and the deaf to hear. When Christ came into the flesh he set this work going, and it continues in Christendom day for day till the world’s end. For this task Christ left us designated instruments: holy baptism, the blessed Sacrament, the Word and absolution, and whatever else belongs to the ministry of preaching, in order to enable us to destroy the devil’s kingdom, to take from him his captives and cast him out of people. That promise is written in Isaiah 55:11: Verbum meum non redibit vacuum, “[My word] shall not return unto me void.” Just as rain fructifies the dry land, causing it to become green and alive, so God’s Word produces fruit wherever it comes. The Holy Spirit accompanies the Word, to enlighten, kindle faith, cleanse, and free people from the devil’s power and rule.
So what that the world takes no note of it! That was true then when Christ personally accomplished it. For the world is not worthy of seeing the smallest spark of God’s wondrous signs and works, but deserves to be blind, senseless, and deaf; for it dishonors, reviles, and slanders the Lord Christ as we see here. We Christians, however, who have and believe the Word should see, know, and be comforted in our hearts that god has vested us with the power here upon earth to continue to drive out the devil also now – indeed it is our duty! – both spiritually and physically.
Every child that comes into this world is born into the kingdom of the devil, the lord of death, who exercises his sway through sin’s tyranny. But upon Christ’s command we bring a child to holy baptism, speak the words of promise which he commanded, and the child is born anew into God’s kingdom; and the devil must yield and get out. God’s grace, through Christ, is spoken by God to the child, inasmuch as he or she is baptized into Christ’s death. When a person whom the devil has greatly overwhelmed and seared with many accusations comes to me with heavy heart and troubled conscience seeking comfort and instruction, I have the mandate, as does every Christian, to comfort my brother and pronounce God’s grace, for Christ’s sake, upon him. The devil must yield, not to me, a poor and wretched sinner, but to the Word which the Lord Christ left us upon earth. When your conscience is weak and terrified, therefore, and you are unable to grasp tightly enough the comfort that God graciously wants you to have, the forgiveness of sins, then know that Christ has given the Lord’s Supper, his true body and blood to eat and to drink, so that you have no reason further to doubt that his body was given for your sins and his blood poured out for your transgressions. Where such faith and trust are present, there it is impossible for the devil to dwell and hold sway.
This work, therefore, must continue apace in Christendom, in order to drive the devil out by the finger of God. Christ began it, as St. Paul states in Acts 10:38, “[Jesus] went about doing good, healing all that were oppressed by the devil; for God was with him.” The Christian church continues this work until the world’s end, indeed more and greater works than those Christ did, as he himself promised (John 14:12): “Verily, verily, I say unto you, he that believeth on me, the works that I do shall he do also; and greater works than these shall he do; because I go unto my Father.”
Martin Luther, House Postil for the Third Sunday in Lent (Luke 11:14-28)