1 Paul, an apostle of Jesus Christ by the will of God, and Timothy our brother, To the church of God which is at Corinth, with all the saints who are in all Achaia:
by the will of God,
Paul became an apostle “by the will of God.” Receiving apostleship is something that God provides; it is not something a Christian leader earns. It does not come by fasting, prayer, or spirituality. It is a sovereign gift from the Holy Spirit (1 Co 12:11). It was not by chance, accident, or luck that Paul became an apostle; it was by means of the will of God. Apostles do not become apostles because they decide to do so. It is because God appoints them as such (Ga 1:15-16; Ac 9:15-16). The will of God should be the concern of every believer (1 Th 5:18; 1 Ti 2:4; 2 Pe 3:9).
and Timothy our brother,
Upon writing Second Corinthians, Paul was with Timothy and Titus in Macedonia. Timothy previously carried First Corinthians to Corinth. In this verse, Paul associates himself with Timothy. Paul trusted Timothy to represent him on many missions (Ac 19:22; Php 2:19-24; 1 Th 3:2; 1 Ti 1:3).
Titus was dispatched by Paul to Corinth to address the problems there and to deliver Second Corinthians to the church. Paul used Timothy first then Titus (Ac 19:22; 1 Co 4:17; 16:10-11).
The Christian life is not dominated by blind chance.
God is sovereign over all our affairs. All of us have come to the point where we cannot understand God’s will for our lives. We cannot rationalize what has happened to us. There are times whereby we must leave ourselves entirely in the hands of God. We trust Him unreservedly to guide us each step of the way. The apostle Paul himself faced many difficult days, but God led him all the way.