6:1 Since God appeals to the unsaved through heralds of the gospel (5:20), the herald is in that sense a partner with God in His work of bringing people into final reconciliation.198Evangelism is a joint effort of the Lord and His human ambassador. Paul went beyond that specific function of an ambassador and, for God, also appealed to his Christian readers. In addition to responding to the call to be reconciled to God, they also needed to respond to another call. They needed to make sure that they were responding to God's grace as well.
Paul's readers had received God's grace when they had heard the gospel message. Now Paul urged them to respond to it so God's gracious bestowal would not have been in vain. God gives grace to all people throughout their lives, but He gives more grace at the moment of conversion and from then on. It is not clear which manifestation of grace Paul had in mind, the grace the Corinthians received at conversion or the subsequent grace. I think he probably had both in mind and spoke of their response to divine grace generally since he did not clearly identify the past or the present manifestation. Receiving God's grace in vain would be not allowing it to have its divinely intended result in their lives. In the context, conflict between some of the Corinthians and Paul resulting in the discrediting of the gospel ministry seems to be in view (v. 3). More generally, disunity among believers frustrates God's desire and His provision of grace (help). Most broadly, any disobedience to God's will frustrates His grace (cf. 7:1; 11:4; 12:20-21).
"The explanation which in our judgment is most satisfactory, and which seems best to fit the broad context in which this verse is found, is that Paul is here thinking in terms of the judgment-seat of Christ, before which the works of every Christian will be made manifest (5:10)."199
6:2 As he begged unbelievers to receive God's reconciling grace (5:20), Paul now urged his readers to respond quickly and positively to God's grace to them. Paul quoted Isaiah 49:8 to stress the importance of responding immediately. The "acceptable time"will not last forever. In the context of the Isaiah quotation, God addressed His Servant whom the nations had despised promising eventual vindication and urging Him to restore His people. The parallel with Paul and the Corinthians' ministry is obvious. Rather than squabbling among themselves over Paul the readers needed to get on with the ambassadorial work that God had given them to do.
6:3 The Corinthians should not and Paul tried not to give any cause for others to stumble because of their ministry. Obviously we cannot prevent all criticism of our ministry because there may be some who take offense without good reason. Still we should do everything we can to make sure we do not give anyone cause for justifiable criticism.
6:4-5 Paul proceeded to describe positively how he had conducted himself to prove that his own reception of God's grace had not been in vain. He commended and defended his ministry to provide the faithful Corinthians with more ammunition to rebut his critics. Note that he referred to his actions rather than his words. He cited three groups of trials, and there are three kinds of trials in each group. These he prefaced with a claim to patience (steadfast endurance), an extremely important quality in an ambassador of Christ.
