From the Word
12 So then, brethren, we are debtors, not to the flesh, to live according to the flesh— 13 for if you live according to the flesh you will die, but if by the Spirit you put to death the deeds of the body you will live. 14 For all who are led by the Spirit of God are sons of God.
Romans 8:12–14, RSV
Like ourselves, Paul had to deal with two classes of people, the true and the false Christians. There is not so much danger from the adversaries of the doctrine; their opposition is so open that we can readily beware of them. But since the devil sows his seed among us who are called Christians and boast of the gospel, it behooves us to take heed of those who claim to be Christians. It is easy enough to boast of God and of Christ and of the Spirit. But whether such boasting has any foundation depends on whether or not the Spirit so works and rules in us as to subdue and mortify sin. For where the Spirit is, there assuredly he is not idle, nor powerless. He proves his presence by ruling and directing man and prevailing on him to obey and follow his promptings.
To be “led by the Spirit of God” means to be given a heart which gladly hears God’s Word and believes that in Christ it has grace and the forgiveness of sins; a heart which confesses and proves its faith before the world; a heart which seeks, above all things, the glory of God, and endeavors to live without giving offense, to serve others and to be obedient, patient, pure and chaste, mild and gentle; a heart which, though at times overtaken in a fault, and may stumble, soon rises again by repentance and ceases to sin. All these things the Holy Spirit teaches one if he hears and receives the Word, and does not willfully resist the Spirit.
The devil, who is also a spirit, persuades the hearts of the worldlings; but it soon becomes evident that his work is not that of a good or divine spirit. For he leads men to do the reverse of that which the Spirit of God leads them to do; they find no pleasure in hearing and obeying God’s Word, but despise God, and become proud and haughty, avaricious, unmerciful. Let every one therefore take heed that he deceive not himself. For there are many who claim to be Christians and are not. We perceive this from the fact that not all are led by the Spirit of God.
Luther, Martin, and John Sander. Devotional Readings from Luther’s Works for Every Day of the Year. Augustana Book Concern, 1915, pp. 299–300.