The Gospels of Matthew, Mark, and Luke all mention that Jesus was crucified between two criminals. Here are the relevant passages:
* Matthew 27:38: "Then two robbers were crucified with him, one on the right and one on the left."
* Mark 15:27: "They crucified two rebels with him, one on his right and one on his left."
* Luke 23:33: "When they came to the place called the Skull, they crucified him there, along with the criminals—one on his right, the other on his left."
John's Gospel does not explicitly mention robbers, but it does mention that Jesus was crucified with two other men, one on either side.
* John 19:18: "Here they crucified him, and with him two others—one on each side and Jesus in the middle."