"The Call to Witness" represents Calvin's exposition of 2 Timothy 1:8-9, which reads as follows in the ESV: "Therefore do not be ashamed of the testimony about our Lord, nor of me his prisoner, but share in suffering for the gospel by the power of God, who saved us and called us to a holy calling, not because of our works but because of his own purpose and grace, which he gave us in Christ Jesus before the ages began. . . ." In his exposition, Calvin encourages and challenges Christians to preach the Gospel despite threat of persecution or discomfort. He emphasizes God's care for us, that God strengthens us and is powerful and faithful to us. Several times Calvin underscores God's goodness, particularly in His choosing to save helpless sinners; and so we are. Echoing Paul's words in the passage above (and in Ephesians 1:4ff and 2:8-9), Calvin declares that God's calling of us to salvation was merely because of His grace and purpose, not any consideration of our works or dignity. Calvin states: "God never went farther than Himself, when He chose us to salvation. For He saw that there was nothing but condemnation in us: therefore He contented Himself, by mere grace and infinite mercy, to look upon our misery, and help us; although we were not worthy." So in this sermon, we have an ironic but biblical message: God in His goodness elected us to salvation, and we ought to share the Gospel; for He will help us and take care of us, and it would be unthankfulness on our part not to share the Gospel.
I say that this is an ironic message because many have claimed that the Calvinist doctrine of election precludes evangelism. But the title and content of Calvin's sermon highlight the importance of evangelism even while he preaches that God has chosen people to salvation. He says: "If the gospel be not preached, Jesus Christ is, as it were, buried. Therefore, let us stand as witnesses, and do Him this honor, when we see all the world so far out of the way. . . ." Indeed, as Paul writes in Romans 10:14-17 (ESV), "How then will they call on him in whom they have not believed? And how are they to believe in him of whom they have never heard? And how are they to hear without someone preaching? And how are they to preach unless they are sent? As it is written, 'How beautiful are the feet of those who preach the good news!' But they have not all obeyed the gospel. For Isaiah says, 'Lord, who has believed what he has heard from us?' So faith comes from hearing, and hearing through the word of Christ." Calvin stands with Paul in promoting evangelism.
Revel in the grace of God, and do not be ashamed of it. Consider Calvin's words in "The Call to Witness": "It is true, God calleth us at this day, but His election goeth before; yea, and God chose us without any respect to our works, as we could have done nothing before: but we are debtors to Him for all; for He drew us out of the bottomless pit of destruction, wherein we were cast, and past all hope of recovery. Therefore, there is good reason for us to submit ourselves wholly to Him, and rely upon His goodness, and be thoroughly ravished with it."