A mediator is sometimes needed to help two parties in conflict reach an agreement. When a brother in Christ has sinned against me and will not listen to me alone, Jesus instructed me to get one or two more to arbitrate in the matter (Mt. 18:16).
The book of Philemon presents an occasion where Paul functioned as a mediator between Onesimus, a slave, and his master, Philemon, so that their relationship would be that of beloved brothers (v. 16). Onesimus had not left Philemon’s house on good terms; he was an “unprofitable” servant (v. 11) and may have wronged his master or stolen from him in some additional way (v. 17). Leaving Philemon, Onesimus eventually came in contact with Paul in prison. Paul converted Onesimus to Christ, and then sent him back to Philemon with this letter preserved for us in the New Testament in which Paul appealed to Philemon to receive Onesimus back (vv. 10-12). Paul wanted Onesimus to stay with him, but desired Philemon’s consent first (vv. 13-14). Paul had confidence that Philemon would not only receive Onesimus—which would be fitting in obedience to apostolic teaching in regard to the forgiveness of sins—but would do even more than what Paul had said (vv. 8, 21). Perhaps the greatest expression of Paul’s mediation is his statement in verses 17-19 of the epistle, “If then you count me as a partner, receive him as you would me. But if he has wronged you or owes anything, put that on my account. I, Paul, am writing with my own hand. I will repay—not to mention to you that you owe me even your own self besides.” Paul was so desirous of peace between the two that he puts the debts of Onesimus on his own account and promises to repay, even though he could have demanded that Philemon owed him.
In regard to our relationship to God, the Bible clearly teaches, “For there is one God and one Mediator between God and men, the Man Christ Jesus, who gave Himself a ransom for all, to be testified in due time,” (1 Tim. 2:5-6). Our sins cause us to be at odds with God (Isa. 53:1-2; Rom. 3:23). Jesus is the mediator who is both God and man; He understands both parties (Jn. 1:1-3, 14; Phil. 2:5-7; Heb. 2:14; 4:16; 5:1-2). The debt we owe to God because we have wronged Him with our sins was placed on Jesus’ account at the cross (1 Pet. 2:24). Similar to how Abraham offered up Isaac in his heart before the act was ever carried out (Gen. 22:10-12; Heb. 11:17-19), God has allowed man to be reconciled to Him throughout time based on the fact that in His mind sins would be placed on Jesus’ account (Rom. 3:24-26; Gal. 3:13). The preaching of Christ as this great mediator was “testified in due time” when the apostles proclaimed it at the inauguration of the Christian era. No doubt Paul had learned to seek reconciliation with those at enmity because of the great love He saw in God bringing man back to Himself through Christ: “Now all things are of God, who has reconciled us to Himself through Jesus Christ, and has given us the ministry of reconciliation, that is, that God was in Christ reconciling the world to Himself, not imputing their trespasses to them, and has committed to us the word of reconciliation” (2 Cor. 5:18-19). Jesus, as the Mediator of the New Testament (Heb. 8:6; 9:15; 12:24) continues to function as the go-between to continually give us peace with God through His blood so that we are on speaking terms with the Father. That God’s love has provided such mediation in Jesus should compel us to live righteously, “For He made Him who knew no sin to be sin for us, that we might become the righteousness of God in Him” (2 Cor. 5:21).