Verse 1
workers together -- with God (Acts 15:4; 1 Corinthians 3:9).
appeal [beseech, entreat] -- 2 Corinthians 5:20; He is describing his ministry, not exhorting directly.
you also -- rather, "WE ALSO (as well as God, 2 Corinthians 5:20) beseech" or "entreat you": 2 Corinthians 6:14-15, on to 2 Corinthians 7:1, is part of this entreaty or exhortation.
grace -- The Greek word used here, charis, refers in this instance to the unmerited favor God demonstrated in the sacrificial death of Christ (5:14–19). Christ’s death is the reason why people can freely enter into a relationship with God. - FSB
that ye receive not the grace of God in vain -- i.e. that ye make not His kindness in being reconciled to you through Jesus Christ useless by neglecting to walk according to the new life He hath given you in Him ( 2 Corinthians 5:17). CBSC
How could they fail to profit from that grace? By refusing to purify themselves from everything that contaminated body and spirit (2 Corinthians 7:1; 2 Corinthians 12:20-21), by allowing a chasm to develop between faith and conduct, or by embracing a different gospel (11:4), one based on observing the law as the ground of acceptance before God. EBC
in vain -- by making the grace of God a ground for continuance in sin (2 Corinthians 6:3). By a life of sin, showing that the word of reconciliation has been in vain, so far as you are concerned (Hebrews 12:15; Judges 1:4). "The grace of God" here, is "the reconciliation" provided by God’s love (2 Corinthians 5:18-19; compare Galatians 2:2). - JFB