According to Matthew 26:56, as soon as Jesus was arrested,
"...all the disciples left Him and fled."
They wanted no part of the torturous exercise that Christ was about to endure. And apparently their cowardice did not end there. In his account of the gospel, John records in 20:19 that Jesus found the disciples behind closed doors for fear of the Jews.
"So when it was evening on that day, the first day of the week, and when the doors were shut where the disciples were, for fear of the Jews, Jesus came and stood in their midst and said to them, 'Peace be with you.'" (John 20:19)
"After eight days His disciples were again inside, and Thomas with them. Jesus came, the doors having been shut, and stood in their midst and said, 'Peace be with you.'" (John 20:26)
Even after eight days of thinking, reasoning, and considering what had happened Jesus still finds them behind locked doors for fear of the Jews. Even after eight days of pondering the power of the risen Lord they are still trembling.
Why would eleven men that are hiding in a locked room soon be preaching to the people they are hiding from? According to Josephus and other ancient secular historians, eleven of the twelve apostles died as martyrs. Why would these men be hiding one day, and dying the next? I can only explain it one way--stated above by John--Jesus came and stood in their midst.
What about Peter? In Matthew 26, Peter is described as denying Christ to a servant-girl. If he is not willing to proclaim his Lord to a servant, how much less likely would he be to proclaim the Messiah to the Jewish leaders, whom he feared? Why would Peter be preaching to these very people just a few days later? Perhaps the answer is found in 1 Corinthians 15:5,
"He appeared to Cephas..."
What about James?
"For not even His brothers were believing in Him." (John 7:5)
In this passage James, the brother of Jesus, is depicted as an unbeliever, but later we read in James 1:1 that he considers himself a bond-servant of God and the Lord Jesus Christ. In Galatians 1:19 Paul refers to James as an apostle. What caused this dramatic change in attitude? Could it be 1 Corinthians 15:7,
"then He appeared to James..."