Command therefore that the sepulchre be made sure until the third day, lest his disciples come by night, and steal him away, and say unto the people, He is risen from the dead: so the last error shall be worse than the first.
Tell them to secure the tomb until the third day, to prevent his followers from stealing him during the night and claiming he has risen from the dead. This could lead to more confusion and a greater mistake.
* Work in progress - there may be occasional inaccuracies