The best planned plan failed - He arose!

MATTHEW 28:11

1 Now while they were going, behold, some of the guards came into the city and reported to the chief priests all the things that had happened.

In the Jews' efforts to prevent anything from happening that would cause people to believe that Jesus was resurrected, they gave one of the surest proofs of His resurrection. They sealed the tomb so it would be obvious if it had been opened and they obtained a guard of soldiers to protect it.

This removes all doubt that the followers of Jesus could have stolen His body. Therefore, the enemies of Jesus became a historical witness that Jesus literally rose from the dead.

The guards told the chief priests everything that happened at the tomb. This means that they had a complete account of the earthquake, the angels rolling away from the stone, and the angels giving the message to the women that Jesus was alive from the dead. 

They may have even seen Jesus walk out of the tomb.

The very ones that the Jews had secured to guarantee there would be no rumors of Jesus being raised from the dead, became the first witnesses and heralds of the resurrection. Yet, with the testimony of impartial, non-religious eyewitnesses, they chose not to believe (Lk. 16:31).