Chapter six contains two primary sections. As Paul wrapped up the self-defense of his authority and ministry that he had spent the past several chapters declaring, he presented the Corinthians with two challenges. First, he challenged them to not turn away from the message he had presented (2 Corinthians 6:1-10).
“To receive the grace of God in vain” does not have anything to do with losing their salvation. If we were to remove the chapter and verse divisions, Paul had just explained that the purpose of their salvation was “so that in him we would become the righteousness of God” (5:21). To receive God’s grace without growing in righteousness, he explained, would be to receive it “in vain” or “for no purpose.” He urged them to reconsider their rejection of his ministry and message, because he and his team had “commended [themselves] in every way,” risking life and limb to make sure the Corinthians had the truth. “Please,” he begged, “reciprocate our love for you by turning your affection back toward us again” (2 Corinthians 6:11-13).
Paul’s second challenge was toward their thinking and associations (2 Corinthians 6:14-18). For some reason they had welcomed Paul’s accusers and false teachers with open arms (see 2 Corinthians 11:4). They had no spiritual discernment and apparently were willing to listen to whoever was right in front of them. Rather than simply saying, “Don’t associate with them!”, Paul challenged their thinking. “Consider this: what partnership is there between righteousness and lawlessness…Christ with Belial…a believer with an unbeliever…the temple of God with idols?” (2 Corinthians 6:14-16) It seems he thought they could answer that well enough; there is nothing in common at all.
Paul would not always be there to tell them which individual to listen to; instead, they needed to be able to identify false doctrine and choose to disassociate from it. Paul reminded them that “we are the temple of the living God,” home of the indwelling Spirit (2 Corinthians 6:16-18). Because of this relationship and status with God, they had no business attaching themselves to anything that goes against God, his character, or his truth.
This is a very practical truth that is always relevant. Every believer needs to study the Scriptures and know the truth well enough to discern between true and false teachers, good and evil peers, and sinful and righteous lifestyles.