How can we be sure that God calls His people?

In the sermon, the preacher emphasizes that the calling of God is not a result of human effort or persuasion, but a sovereign act of God that brings about true belief and repentance. In 1 Corinthians 1:26-27, Paul points out that God has chosen the foolish things of the world to confound the wise. This divine calling is powerful and life-transforming, ensuring that those whom God calls will respond to the gospel with faith. The believer's assurance lies in God's effective call, which is revealed through a genuine change in heart and the desire to pursue Christ.