Christ indeed from death is risen, our new life obtaining
The resurrection of the dead was expressly taught by Jesus (~ John 5:28-29), and defended against the disbelief of the Sadducees.
Paul of Tarsus places the general resurrection on the same level of certainty with that of Christ’s Resurrection:
“If Christ be preached, that he rose again from the dead, how do some among you say that there is no resurrection of the dead? But if there be no resurrection of the dead, then Christ is not risen again. And if Christ be not risen again, then is our preaching vain, and your faith is also vain” (1 Corinthians 15-12:15)
There are those who argue that the apostles, and Jesus' other close friends such as Mary of Magdala were eager to prove the resurrection of their friend, Jesus of Nazareth...
...then there is the matter of...Paul of Tarsus.
....Prior to his encounter with the Risen Christ on the road to Damascus, Paul of Tarsus had been fanatical in his pursuit of The Nazarenes, punishing them for their fellowship with Jesus of Nazareth. Tradition teaches us that Paul was probably present at the martyrdom of the Apostle Stephan.
From an enemy of The Christ becoming one of His most devoted followers the result of the revelation on his journey to Damascus to detain Nazarenes, evidences that the resurrection of The Christ had been embraced by Paul of Tarsus who had been a bitter enemy of everything Jesus of Nazareth represented.