Luke 23:18-25
He released the man who had been thrown into prison for insurrection and murder, for whom they asked, but he delivered Jesus over to their will. (Luke 23:25 ESV)
Barabbas was a known murderer. He had led an attempt at a full blown uprising. Usually that type of activity was met with swift and brutal retribution in the Roman world. However, for some reason Barabbas had been left on prison to rot. When it would have came time for him to have faced justice, Jesus was there to take his place.
Jesus took his place! Barabbas deserved justice. He deserved the full extent of the law, but he didn't face it because Jesus took his punishment.
You and I face our own punishment. We have sinned, we deserve an end that often reflects a lifetime of selfishness and immorality. But Jesus didn't die for your morality. He died to make you family. Why? Because he is more interested in the criminal than the crime. He took the place of a murder.
Regardless of background, moral slant, and failures—Jesus stands in for you. Barabbas' freedom was purchased by the death of Christ. So is ours.