Now it was the custom at the festival to release a prisoner whom the people requested. A man called Barabbas was in prison with the insurrectionists who had committed murder in the uprising. The crowd came up and asked Pilate to do for them what he usually did. “Do you want me to release to you the king of the Jews?” asked Pilate, knowing it was out of self-interest that the chief priests had handed Jesus over to him. But the chief priests stirred up the crowd to have Pilate release Barabbas instead.
“What shall I do, then, with the one you call the king of the Jews?” Pilate asked them.
“Crucify him!” they shouted.
“Why? What crime has he committed?” asked Pilate.
But they shouted all the louder, “Crucify him!”
Wanting to satisfy the crowd, Pilate released Barabbas to them. He had Jesus flogged, and handed him over to be crucified. Mark 15:6-15
Frederick Buechner explains:
"Pilate told the people that they could choose to spare the life of either a murderer named Barabbas or Jesus of Nazareth, and they chose Barabbas. Given the same choice, Jesus, of course, would have chosen to spare Barabbas too.
To understand the reason in each case would be to understand much of what the New Testament means by saying that Jesus is the Savior, and much of what it means too by saying that, by and large, people are in bad need of being saved."