Why did Jesus tell Mary not to touch him?

The original Greek verb, which is usually translated "touch," means also "to cling to, hang on by, lay hold of, grasp, handle." It very well have been that Mary feared that Jesus would leave her to ascend to heaven. His instruction to her "not to touch him" was coupled with the assignment to "go to [his] brothers and say to them, 'I am ascending to my Father and your Father and to my God and your God.'" (John 20:17, Matthew 28:10) Mary would have been thus assured that Jesus still had business on Earth to attend to and therefore would not depart hastily.