...how that Christ died for our sins according to the scriptures; And that he was buried, and that he rose again the third day according to the scriptures: And that he was seen of Cephas, then of the twelve: After that, he was seen of above five hundred brethren at once; of whom the greater part remain unto this present, but some are fallen asleep. - 1 Corinthians 15:3-6
More than five hundred who were now "brethren" (Christians, brothers in Jesus Christ) saw Jesus alive after the crucifixion.
Paul continues in 1 Corinthians 15:7-8:
After that, he was seen of James; then of all the apostles. And last of all he was seen of me also, as of one born out of due time.
So, all of the apostles saw Jesus alive after His crucifixion. Paul also saw Jesus alive after the resurrection.
Cephus (Peter) wrote two epistles, John three, and Paul fourteen. Matthew wrote the Gospel According to Matthew. Luke wrote the Gospel According to Luke and the historical book of Acts, recording the evangelistic work some of the apostles and others. John wrote the Gospel according to John and the Book of Revelation, in addition to his three epistles.
All of these endured severe persecution for their faith in a dead man? No! For a man whom they had seen alive before and after his crucifixion and resurrection!
There is an abundance of evidence that Jesus rose from the dead. What we have seen is evidence both in and out of the New Testament of Jesus' resurrection. Yes, outside, for no one has ever been able to prove that what the New Testament records is untrue. Jesus' body has never been produced. Where is He? The apostles saw Him ascend into heaven where He reigns at the right hand of God (Luke 24:36-53; Acts 1:1-11; 2:22-24; 31-33).
Jesus is alive. He was "...declared to be the Son of God with power, according to the spirit of holiness, by the resurrection from the dead" (Romans 1:4) Do you believe?