2 Corinthians 6 As God’s co-workers we urge you not to receive God’s grace in vain.2 For he says,
“In the time of my favor I heard you, and in the day of salvation I helped you.”
I tell you, now is the time of God’s favor, now is the day of salvation.
Grace is one of the most important words in a Christian's vocabulary. It means God's "unmerited favor" in light of his mercy. It is very similar to mercy which is, "not getting what we deserve." Mercy is God's character by which he offers the free gift of grace. Once we receive God's grace in Christ and believe in His name, we become a believer. We are "born again."
But Paul's purpose in writing to the church of Corinth is to make sure that they don't return to their former ways and their practice of idolatry. On top of that some were questioning whether Paul was a true apostle. In the verses following, Paul shows all the adversity and hardships he went through to preach the gospel.
So what does he mean by the command, "do not receive God's grace in vain." Primarily Paul is saying that when you have become a new creation in Christ, live in this new reality empowered by the Holy Spirit, who lives within us. Though the believers in Corinth were saved, there was still temptation in the city to return to their former ways. Some of the immorality in the culture around them had seeped its way back into the church. That is why Paul is so adamant about writing them, and visiting the church every so often to remind them of these truths.
"Receiving God's grace in vain" is receiving God's salvation by grace, which delivers one from sin, and then returning right back to it. It is like receiving a gift, but and then throwing it back in the garbage.
How are you tempted to receive God's grace in vain? When we return to sin and conform to the world around us, we are in danger of cheapening God's grace. But God's grace is the gift we receive when we accept Jesus, and live by each day. Every day we can renew this gift, as we live the new life God has called us to live. In His grace, God has also given us spiritual gifts which we get to use to build up His body. As we uses our gifts, the church is God's light in the world. When we live by grace, our lives are being spent on something so much better than what the world offers. Others will experience God's grace through us as we don't receive it in vain. This is what it means to be a Christian, and Paul does not want the Corinthians to waste this precious gift that he was privileged to share with them.