We are to learn from this report of the casting out of a devil the most consoling truth that Christ is the Lord over the devil and his realm; and, further, that this work, then begun in the body, did not terminate, but still continues in the Church of Christ, and will continue until the judgment day. For the accomplishment of this work Christ has instituted the necessary means; namely, Holy Baptism, the Lord’s Supper, the Word and Absolution, also other offices pertaining to the ministry, whereby the devil is to be cast out from the people, so that they may become free from his thralldom and that his kingdom may be destroyed. For it is plainly written in this respect: Verbum meum non redibit vacuum – My Word shall not return void. As the rain which falls upon dry land produces vegetation and blossoms, thus does the Word of God, most assuredly, produce fruit in some hearts. The Holy Spirit is connected with the Word to illumine, incite and purify the hearts, that they may be set free from the tyranny and oppression of the devil. This transaction is not visible to the outward eyes, as it was when Christ cast out the devil; it may be entirely imperceptible to the world, which is indeed not worthy to see the least spark of divine light and power, and which is blind, reviles, abuses and defames that which is good, as it did even here in the presence of Christ. We, however, who have and believe the Word, ought to perceive and know this truth which is so full of comfort, that God has ordained among us the means whereby we can and must continually cast out devils.  (Luther’s House Postil, Sermon for Oculi, Volume 1, p. 272-273)

One without faith would never have acted thus, but would have concluded: It is of no use to present my request before Him; I am in the clutches of the devil beyond all hope; let His own people come to Him; them will He hear, but not me. Whoever has no faith is utterly unable to pray. The woman is not vexed with doubts as to her privilege of coming to Christ: she does not spend the time in debating the question, whether she dare come or not; she simply starts upon her way and comes. It is surely a severe and dangerous affliction when the devil prompts the heart to despair of the mercy of God, to refuse to pray to Him, yea, rather to be ready to curse Him, and to think that all is lost and damnation sure. Such wicked thoughts deter an inexperienced heart from prayer and throw it into despondency. This story is therefore of great value for us, and written on our account, so that we might know how to meet the enemy when he comes and says:

“You are no Christian, your prayer is in vain.” Mind not such insinuations, but answer boldly: I care not who I am. I know that I am a sinner, but I also know that Christ my Lord is holy, ever just and merciful. Therefore I will call unto Him without hesitation and think of nothing besides; I have no time to debate, whether I am one of the chosen or not. This much I know: I need help, and on that account I come, humbly seeking it. If we are thus disposed in mind, we follow the example of our Gospel aright. The woman was a heathen, and, aware of that, she had to conclude that she did not belong to the chosen people; she swallows, however, contentedly this big and bitter morsel, still praying unto Christ with much earnestness. Go and do likewise; say: O Lord, here I come, in want of everything. Give me what I need through Thy Son, my Lord and Savior Jesus Christ! Such a struggle of faith, and wonderful exhibition of its nature, is manifested in this heathen woman.  (Luther’s House Postil, Sermon for Reminiscere, Volume 1, p. 266-267)