In a section of Paul’s Letter to the Galatians explaining how Christians should handle the freedom they have in Christ, there is a very practical contrast of two modes of life: walking by the Spirit and walking according to the flesh.
Paul introduces the contrast in 2:20, when he says “I have been crucified with Christ; and it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God who loved me and gave Himself up for me.” There is more to life here than simply living in the flesh.
He questions in 3:3, “Are you so foolish? Having begun by the Spirit are you now being perfected by the flesh? The Galatian believers were falling into an error regarding their daily walk with God. They had rightly come to be saved by grace through faith, and were thus regenerated by the Holy Spirit, but they were walking as if their growth would come simply from external obedience to rules and regulations. Specifically, some were trying to place themselves under elements of the Mosaic Law, so that they could meet a standard that was just a little higher than the standard of others. Even for those (in earlier generations) who actually lived under Mosaic Law, their salvation was not through obedience to the Law. In Matthew 5-7 Jesus explains that righteousness comes not from external obedience, but is demonstrated by internal character (which of course, we might expect to have an effect on external behavior). This was one reason the Law couldn’t save anyone: it was only a measuring stick to show the need for the righteousness that comes through redemption (Gal 3:24).
Those Galatians, then, that had fallen into a legalistic approach to their walk, were not walking according to the Spirit, but were instead depending on their own flesh. Just as Paul illustrated from his own life so vividly in Romans 7, for the Christian, there is a battle between the spirit within them and their flesh. He explains in Galatians 5:17 that “the flesh sets its desire against the Spirit, and the Spirit against the flesh.” In Romans 7, Paul contrasts the flesh with the believer’s own spirit, while in Galatians 5, the Spirit he is talking about is the Holy Spirit, and not just the newly alive spirit within us (see Gal 3:2, 14, 6:8). So Paul presents a model for Christian living: if we depend on ourselves, we will not walk properly. But if we depend on God (specifically, the Holy Spirit who indwells us), then we can walk properly.
The contrasting walks are identified in 5:16 – walk by the Spirit, or carry out the desire of the flesh. These two are in opposition to one another, are not compatible, and ultimately have diametrically opposing results (5:17). The deeds of the flesh include a laundry list of dirty laundry: immorality, impurity, sensuality, idolatry, sorcery, enmity, strife, jealousy, outbursts of anger, disputes dissensions, factions, envying, drunkenness, carousing, and things like these…” (5:19-21). Just in case anyone can’t figure out that these are bad things, Paul reminds the readers that these are the natural outworkings of those who are not transferred to God’s kingdom (as in Col 1:13). So how ridiculous would it be for believers – who have been reborn, and transferred to His kingdom above – to behave as those who are dead in their sins (as in Eph 2:1-4), and as those who are not sealed by the Holy Spirit (Eph 1:13-14), and as those who do not have the Holy Spirit dwelling in them (Rom 8:9)?
Instead of fleshly deeds, the Holy Spirit bears fruit in the believer: love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control (5:22-23). But the believer has a responsibility to walk by the Spirit (5:16,25). In 5:16 the term walk is the imperative form of peripateo – meaning walk around. In 5:25 the term translated as walk is stoichomen – which means to conduct oneself, or to go about the course of life. Notice Paul’s play on words in 5:25 – if we live (have our existence by the Spirit), then we should live (conduct ourselves) by the Spirit. It’s kind of a “dance with the one that brung ya” concept.
As Christians, we have new life through Christ, being now children of the Father, and indwelt by the Holy Spirit. Positionally we have been given this incredible spiritual wealth (Eph 1:3), and now, as Paul put it, we need to walk in a manner worthy of that calling (Eph 4:1). Our practice should fit our position. If our practice doesn’t fit our position, it doesn’t change our position, but it creates an absurdity in the life of the believer. As Paul asks in Galatians 3:3, “are you so foolish? Having begun by the Spirit are you being perfected (or completed) by the flesh?”
How then do we walk by the Spirit?
Paul emphasizes to the Galatians that they should walk in the same way they received their position – hearing with faith (3:2). Ultimately what was heard was the word of God (3:5-14). We come to know Him and be reborn by hearing the word of God with faith in Him (as in Rom 10:17, Jn 3:16, etc.). That word is also called the sword of the Spirit (Eph 6:17), and is authored by the Holy Spirit (2 Pet 1:20-21). As Paul illustrates in Ephesians 5:18, the believer should be filled – controlled – by the Holy Spirit, and that happens when we are pouring His word into us, and are submitting to it – hearing God’s word, and responding in faith.
Paul describes this elsewhere as “being transformed by the renewing of your mind” (Rom 12:2), and explains that in that process we are proving what the will of God is (just like as in Eph 5:17) – that which is good, acceptable, and perfect. So we have a choice at every moment. Will we walk by the Spirit as people who are hearing with faith? Or will we walk by the flesh, depending on our own strength and following our own desires? This is a choice that every Christian faces at every moment.