The following is an excerpt from The MacArthur New Testament Commentary on Galatians 5.
For the flesh sets its desire against the Spirit, and the Spirit against the flesh; for these are in opposition to one another, so that you may not do the things that you please. But if you are led by the Spirit, you are not under the Law. (Galatians 5:17–18)
Along with many others in the New Testament, these two verses make it obvious that walking by the Spirit is not simply a matter of passive surrender. The Spirit-led life is a life of conflict, because it is in constant combat with the old ways of the flesh that continue to tempt and seduce the believer. The flesh sets its desire against the Spirit, and the Spirit against the flesh.
A believer who is not actively involved in resisting evil and obviously seeking to do good is not being led by the Spirit, no matter how much he may think he is “surrendered.” The faithful believer is not an observer but “a good soldier of Christ Jesus” who is engaged in the “active service” of his Lord (2 Tim. 2:23–4).
As a repeated warning to believers who were being influenced by the Judaizers, Paul added, But if you are led by the Spirit, you are not under the Law. To live under the Law is to live by the flesh, even when one is not actually committing sin, because that is the only avenue available to the legalist. The flesh is powerless to fulfill the Law, and the Law is powerless to conquer the flesh. Rather, “sin, taking opportunity through the commandment, produced in me coveting of every kind; for apart from the Law sin is dead. And I was once alive apart from the Law; but when the commandment came, sin became alive, and I died; and this commandment, which was to result in life, proved to result in death for me; for sin, taking opportunity through the commandment, deceived me, and through it killed me” (Rom. 7:8–11).
In his Pilgrim’s Progress, John Bunyan describes Interpreter’s house, which Pilgrim entered during the course of his journey to the Celestial City. The parlor of the house was completely covered with dust, and when a man took a broom and started to sweep, he and the others in the room began to choke from the great clouds of dust that were stirred up. The more vigorously he swept, the more suffocating the dust became. Then Interpreter ordered a maid to sprinkle the room with water, with which the dust was quickly washed away. Interpreter explained to Pilgrim that the parlor represented the heart of an unsaved man, that the dust was original sin, the man with the broom was the law, and the maid with the water was the gospel. His point was that all the law can do with sin is to stir it up. Only the gospel of Jesus Christ can wash it away.
“The power of sin is the law,” Paul declares; “but thanks be to God, who gives us the victory through our Lord Jesus Christ” (1 Cor. 15:56).
To be led by the Spirit is the same as walking by Him (vv. 16, 25) but carries additional emphasis on His leadership. We do not walk along with Him as an equal, but follow His leading as our sovereign, divine Guide. “For all who are being led by the Spirit of God, these are sons of God,” Paul says (Rom. 8:14). The converse is also true: Those who are sons of God are led by the Spirit of God. Believers do not need to pray for the Spirit’s leading, because He is already doing that. They need to seek for willingness and obedience to follow His leading.
When Christ enters a person’s life, the Holy Spirit enters simultaneously (cf. Rom. 8:9). And the moment He enters He begins to lead God’s newborn child in the way of freedom (Gal. 5:1), holiness (Gal. 5:16), truth (John 16:13–15), fruitfulness (Gal. 5:22–23), access to God in prayer (Eph. 2:18), assurance (Rom. 8:16), witnessing (Acts 1:8), and submissive joy (Eph. 5:18–21).
No wonder Paul rejoiced that “what the Law could not do, weak as it was through the flesh, God did: sending His own Son in the likeness of sinful flesh and as an offering for sin, He condemned sin in the flesh, in order that the requirement of the Law might be fulfilled in us, who do not walk according to the flesh, but according to the Spirit” (Rom. 8:3–4).