Now on the next day, the day after the preparation, the chief priests and the Pharisees gathered together with Pilate, and said, “Sir, we remember that when He was still alive that deceiver said, ‘After three days I am to rise again.’ Therefore, give orders for the grave to be made secure until the third day, otherwise His disciples may come and steal Him away and say to the people, ‘He has risen from the dead,’ and the last deception will be worse
than the first.”
Jesus' enemies admit that He is dead, for they recall the words He said, "when He was still alive." They don't believe in the "Swoon Theory," that says Jesus never really died, but just "swooned" on the cross, and then somehow revived in the tomb.
A humorous letter to the editor of a Christian magazine accurately evaluated the "Swoon Theory":
Dear Eutychus: Our preacher said, on Easter, that Jesus just swooned on the cross and that the disciples nursed Him back to health. What do you think?
Dear Bewildered: Beat your preacher with a cat-of-nine-tails with 39 heavy strokes, nail him to a cross; hang him in the sun for 6 hours; run a spear through his heart; embalm him; put him in an airless tomb for 36 hours and see what happens.
"A guard was posted and the tomb was secured with an official Roman seal (v.66). The religious and political leaders did their very best to make sure that the body of Jesus remained in the tomb, but they were attempting the impossible. Death could not hold the sinless Son of God in its grasp, and on the third day He rose just as He said He would." (Herbert Vander Lugt)