And in Jesus Christ, His only Son, our Lord, who was conceived by the Holy Spirit, born of the virgin Mary, suffered under Pontius Pilate, was crucified, died, and was buried. He descended into hell. The third day He rose again from the dead. He ascended into heaven and sits at the right hand of God the Father Almighty. From thence He will come to judge the living and the dead. What does this mean? ...that I may be His own and live under Him in His kingdom and serve Him in everlasting righteousness, innocence, and blessedness, just as He is risen from the dead, lives and reigns to all eternity. This is most certainly true. (The Small Catechism: The Second Article)
Alleluia! Christ is risen! In the Name of Jesus. The “this is most certainly true” is what the world questions. How can you know it's true? Why do you believe all that old Bible stuff? Myths. Stories. Religious nonsense. The “this is most certainly true” comes from Easter! We believe what the Bible says because on the third day Jesus was alive. People saw Him dead. They saw Him alive. The tomb was empty. Upon this fact of Christ's being alive the third day after being dead all our hope and comfort as Christians is built.
St. Paul was right: If Christ didn't actually rise from the dead, Christians are about the saddest and most pathetic people around, believing such a lie. (1 Corinthians 15). But Paul also knew that Christ was alive, not only because He had appeared to Paul, but also because so many other disciples had seen Him alive. There were eyewitnesses.
Now, you may not have seen Jesus with your eyes, but you have the eyewitness testimony written down. We call it the New Testament, written by those who had seen and heard Jesus. Some had seen Him die. Most had seen Him alive again. His resurrection is a fact.
But Jesus' resurrection didn't happen just so we can say we were right and the scoffers were wrong. It happened so that we no longer ever have to fear death. Ever. Death has been defeated. There IS something beyond the grave: everlasting life with Christ. His coming out of the tomb on Easter is a foreshadowing of your coming out of your grave on the last day. Just as He rose, you will rise from the dead, too. Your baptism says that His resurrection has become yours. This is most certainly true, because Christ is risen!
Had Christ who once was slain, Not burst His three-day prison, Our faith had been in vain: But now has Christ arisen, arisen, arisen; But now has Christ arisen! (This Joyful Eastertide, LSB 482:Refrain)