It is important to know how secure Jesus’ grave was from outside influences. The tighter the security, the less likely the body could have been tampered with. Archaeologists have been able to determine from excavations of first-century sites how Jesus’ tomb was probably constructed.
There was likely a slanted groove that led down to a low entrance and a large disk-shaped stone was rolled down this groove and lodged into place across the door. A smaller stone was then used to secure the disk. Although it would be easy to roll this big disk down the groove, it would take several men to roll the stone back up in order to reopen the tomb. In short, it was quite secure.
In addition to the physical weight of the rock at the tomb’s entrance, guards stood watch around the tomb. In fact, Matthew reports that when the guards reported Jesus’ resurrection to the chief priests, the Jewish leaders paid them to say that they were sleeping while the disciples moved the large rock to steal the body (see Matthew 28:11–15).
Adapted from interview with Dr. William Lane Craig