All this is from God, who reconciled us to himself through Christ and gave us the ministry of reconciliation: that God was reconciling the world to himself in Christ, not counting people’s sins against them. And he has committed to us the message of reconciliation. (2Co 5:18-19 NIV)
But without your consent, I wanted to do nothing, that your good deed might not be by compulsion, as it were, but voluntary. For perhaps he departed for a while for this purpose, that you might receive him forever, no longer as a slave but more than a slave– a beloved brother, especially to me but how much more to you, both in the flesh and in the Lord. 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. Yes, brother, let me have joy from you in the Lord; refresh my heart in the Lord. (Phm 1:14-20 NKJ)
The reason why Jesus died on that cross was to reconcile man to God. Through his death and resurrection reconciliation then becomes a ministry of the Church. In the book of Philemon Onesimus is a runaway slave, possibly from Colossae. Heading to Rome, he finds Paul, a prisoner himself, under house arrest. Paul shares the gospel with Onesimus, and he becomes a valuable member of the Christian community and a great help to Paul. However, Onesimus has to be returned to his master. Paul writes the Philemon, himself a Christian, and tells him that Onesimus is coming back a changed man. Still a slave, yes, but also an Ambassador for Christ, carrying not only the letter to Philemon but also a letter to the Colossian church. Paul asks Philemon to view Onesimus differently, he once was just a slave; now he is a brother in Christ. Paul as a minister of reconciliation even offers to pay Philemon any out of pocket expenses.
I realize that today, the whole idea of slavery is appalling, but under Roman law, it was common practice. For Paul to keep Onesimus would have made Paul a law breaker. Instead, Paul stands in between the two and stretches out both arms, a picture of the cross.