If you look at the apostles and the followers Jesus at the time of His death and resurrection, they were so dramatically changed that there had to be some validity to their claims. Yes, one of Jesus’ inner circle betrayed Him, and the other apostles ran for their lives, even Peter was a coward after he had insisted that he was ready to die for Jesus but he lost heart and denied that he even knew Jesus, but the apostles went through a dramatic change after the resurrection and after being filled with the Spirit. They were standing face to face with the ones who had actually crucified Jesus and they were as bold as lions and became unstoppable in their determination to sacrifice everything for Jesus – even their lives! That's powerful! Even after they were imprisoned and threatened and forbidden to speak in the name of Jesus, the Apostle said to the Jewish leaders (Acts 5:29), “we ought to obey God rather than men.” Yeah, after that they were beaten for disobeying the Jewish leaders’ orders. There was a boldness that came because they really believe that Jesus had risen! Acts 5:42 (Amplified) says, “and every single day in the temple area and in homes they did not stop teaching and telling the good news of Jesus as the Christ.” If these guys had fabricated all of this and had made it all up then they would not have been so bold about it yeah. You won't maintain your lie if you're tortured and if you're beaten and if you're persecuted. You only allow yourself to suffer for truth!
That brings me to the next evidence for the resurrection: the witnesses were willing to die for their claims! History is full of martyrs from different faiths and countless men and women have died for their beliefs (even unknowingly false beliefs) and for that reason it's not significant to just point out that the first disciples were willing to die and even suffer for their faith, but it is significant that while many will die for what they believe to be true, few will be willing to die for what they know to be a lie. This fact is important because the disciples of Christ did not die for something they knew was a lie. They really believed their claims! Peter would have never been hung upside down on a cross for a lie which he had made up. Mark would never have been drug through the streets to his death if he had been defending fiction. James wouldn't have been beheaded for something he knew to be a lie. Thomas wouldn't have been pierced with a Lance for a lie, and yet tradition tells us that all of these men died horrible deaths which makes it worth considering their claims. Thomas was speared to death. Matthew was speared to death. Phillip was tortured and crucified upside down. Bartholomew was skinned alive and then crucified upside down. Andrew was crucified. James, Thaddeus and Simon were all crucified. Why would so many men be willing to die for a lie that they knew was a lie?
Another point of evidence for the resurrection is that Jewish believers changed their day of worship from the Sabbath day which was their day of rest and worship (essential to Jewish life) to Sunday (believed to have been the day of the Resurrection). The Sabbath was the basic way of Jewish life and any Jew who did not honor the Sabbath was guilty of breaking the law of Moses. Yet Jewish followers of Christ began worshiping with gentile believers on a new day – the first day of the week! They replaced the Jewish Sabbath for meeting to worship Jesus on a Sunday. For a Jew this was a major change! Those who believed that Christ had risen from the dead were ready for more than just a renewal of Judaism – Christianity is not an extension of Judaism: they believe that the death and resurrection of Christ cleared the way for a new way of relationship with God not based on the law of Moses.
This was a major shift! Following Christ meant to depart from the Jewish ways of relating to God. We often don't think in terms of history when we're faced with the reality of the gospel. The fact that so many Jews accepted Christ and changed their whole way of life is major! Jesus’ death and resurrection is historical fact. The tomb is empty! Jesus is alive!