“Therefore, we are ambassadors for Christ, God making his appeal through us. We implore you on behalf of Christ, be reconciled to God.” (2 Corinthians 5.20)
Two things stand out to me here: “God making his appeal through us” and “On behalf of Christ.”
First, we hear that the evangelism of Paul and his partners is not the words of a man trying to get people saved. It is God’s appeal through human instruments. God has chosen to make his message known by the preaching of the gospel (cf. Romans 10.17). Thus, our preaching is of necessity while at the same time being guaranteed. God will get his message heard, his appeal made, and it will be by human messengers.
But, this preaching is neither man powered nor solely obedience. Once again, return to Galatians 2.20:
Therefore, we are ambassadors for Christ, God making his appeal through us. We implore you on behalf of Christ, be reconciled to God.
The man that is crucified to self, living in the flesh by faith in Christ and Christ through him, willbe moved to evangelism. Nothing is sheer will, everything is by the heart. And God will guarantee the making of his appeal by controlling the heart of his evangelist.
Second, the call to reconciliation is made “on behalf of Christ.” By the power of God I may love my neighbor and weep, if necessary, over his lostness, but the drive to evangelize him is not wrought of my own benevolence and love but of the will of Christ to reconcile them to God. I alone dictate nothing. God works sovereignly, either sovereignly with me or sovereignly against me. Whichever way, it gets done, even is this may be by way of exposing my own pride.