Paul’s admonition that we walk in the Spirit so as not to gratify the flesh (Gal. 5:16) points to the believer’s ongoing struggle. Already we enjoy salvation, having received the Spirit through faith in Jesus (Eph. 1:13–14). Still, our fleshly nature is not yet obliterated even though our glorification is sure (Rom. 8:1–30). Until death, our evil desires oppose the Spirit (Gal. 5:17), the war growing more heated as the Spirit reveals our sin to us, conforming us to Christ. Martin Luther says, “The more godly a man is, the more does he feel that battle.”
Following the Holy Spirit’s lead, we mortify the flesh (v. 16; see Rom. 8:13) and are not “under the law” (Gal.5:18). Certainly, not being under Torah cannot mean that its ethics are now optional. Otherwise, God denies His own standards, which is impossible (Rom. 7:12; 2 Tim. 2:13). Moreover, Galatians 5:18 in context shows that those not led by the Spirit break the so-called moral laws of the old covenant. The Mosaic law forbids sexual immorality, idolatry (Ex. 20:3, 14), and all the other works of the flesh in Galatians 5:19–21. But to bear the Spirit’s fruit is to fulfill the Law, for love is commanded therein (Gal. 5:22; see Lev. 19:18). Even though we are not “under law,” by the Spirit we live it out.
If those in the flesh and those under the Law are not Spirit-led (Gal. 5:16, 18), then to be under the Law is to be in the flesh. To be under the Law is to repeat the error of the Israelites who in bondage to sin looked to the Mosaic law as an end in itself, not as a guardian to take them to the Messiah (Rom. 6:14–23; Gal. 3:21–26). As Augustine says, people “under the law” are motivated by the Law’s threatened torments, not love of righteousness (Ancient Christian Commentary on Scripture, NT vol. 8, p. 81; hereafter ACCNT). They do the Law outwardly to avoid punishment, not from the heart, the font of impurity (Matt. 5:21–30; 15:18–20). Therefore, they do not see the depth of their iniquity or need of grace.
Yet we are led by the Spirit and know we cannot keep the Law in our own power. We see Torah not as an end in itself, as if we ourselves can through its statutes kill the flesh; rather, seeing our sin defined in the Law, we daily turn to Jesus for pardon, drawing upon the Spirit to crush evil (Rom. 8:5, 13).