The thief at the Cross did not enter paradise by mistake. He had a change of heart. Something real happened in his heart. He saw Jesus as the unblemished Holy one and understood the message of the gospel. The thief understood more about Jesus than the crowds and Pharisees. What Jesus did: His life and miracles changed his heart.
His heart was broken. He did not repent in words, but his heart repented without realizing it. He never recited a prayer of repentance, yet repentance was already at work within him, perhaps before he even recognized it. His heart accepted Jesus as God and King.
When he turned and said, “Jesus, remember me,” he was confessing far more than a request. He was acknowledging Jesus as King and he had a Kingdom. He believed there was a kingdom beyond this life, that heaven was real, and that Jesus (the king) held the authority to welcome him into it.
In those moments, an astonishing work took place in the heart of that dying man. He repented, he accepted Jesus as Lord, and he grasped, in some measure, the sacrifice of Jesus.
So the question turns to us: in your own walk with Jesus, how much did you understand about Jesus and what He has done for you?