A.T. Robertson Commentary Galatians 6:8

"For he that soweth unto his own flesh shall of the flesh reap corruption; but he that soweth unto the Spirit shall of the Spirit reap eternal life." — Galatians 6:8 (ASV)

Corruption (φθοραν). For this old word from φθειρω, see on 1 Corinthians 15:42. The precise meaning turns on the context, here plainly the physical and moral decay or rottenness that follows sins of the flesh as all men know. Nature writes in one's body the penalty of sin as every doctor knows.

Eternal life (ζωην αιωνιον). See on Mt 25:46 for this interesting phrase so common in the Johannine writings. Plato used αιωνιος for perpetual. See also 2 Thessalonians 1:9. It comes as nearly meaning "eternal" as the Greek can express that idea.