John Calvin Commentary Matthew 27:65

"Pilate said unto them, Ye have a guard: go, make it [as] sure as ye can." — Matthew 27:65 (ASV)

You have a guard. By these words, Pilate means that he grants their request by permitting them to post soldiers to keep watch. This permission bound them more firmly, so that they could not escape by any evasion; for though they were not ashamed to break out against Christ after his resurrection, yet with Pilate’s signet they as truly shut their own mouths as they shut up the sepulcher.