What does Galatians 6:8 mean?

In the previous verse, Paul reinforced the universal principle that people reap what they sow in life. Job said something similar, "As I have seen, those who plow iniquity and sow trouble reap the same" (Job 4:8). The crops we get will be decided by the seed we put in the ground. In other words, natural cause and effect still applies, both to the Christian and to the unbeliever.

Paul now clarifies this principle of sowing and reaping, in the context of the Spirit of God. Paul has demonstrated in his letter that it is possible to "sow to the flesh," meaning to invest our lives in serving ourselves, through two different mistakes.

One mistake is that of legalism. The Judaizers were urging the Galatians to trust their flesh in the sense that they wanted them to hope that their attempts to follow the law of Moses would make them justified before God (Galatians 2:4). Paul says to those who would trust their own effort in this way that what they will reap, instead, is corruption. That's because the product of our "flesh," our ability to do good in our own power with our bodies, is poisoned with sin. It can't grow the good crop of righteousness and eternal life.

At the same time, some of the Galatian Christians were apparently "sowing to the flesh" by doing whatever felt good to their bodies. They were indulging in sin. The result would be the same for them as it was for the legalists: a harvest of corruption.

Eternal life is only available through the power of God's Spirit. Those who "sow to the Spirit" in that they are trusting Christ for salvation and receiving God's Spirit will receive eternal life. Then they will continue to live in the strength of God's Spirit and bear the fruit described in Galatians 5:22–23.