What does the phrase, “You reap what you sow,” mean? To reap is “to gather a crop,” and to sow, “to plant seeds.” Throughout scripture, sowing is used as a metaphor for one’s actions and reaping for the results of such actions. The biblical meaning of this phrase comes from a passage in Galatians: “Don’t be misled — you cannot mock the justice of God. You will always harvest what you plant. Those who live only to satisfy their own sinful nature will harvest decay and death from that sinful nature. But those who live to please the Spirit will harvest everlasting life from the Spirit.” (Galatians 6:7-8)

Source: Christianity.com