Jesus said to her, "Mary!" She turned and said to him in Hebrew, "Rabbouni," which means Teacher. Jesus said to her, "Stop holding on to me, for I have not yet ascended to the Father. But go to my brothers and tell them, 'I am going to my Father and your Father, to my God and your God.'" Mary went and announced to the disciples, "I have seen the Lord," and then reported what he had told her. (John 20:16-18)
Jesus tells Mary to stop holding on to Him because He has not yet ascended to the Father. How difficult that must have been for her. Imagine seeing your beloved dead and then He appears alive before you. The first thing anyone would want to do is grab hold and never let go. But Jesus is not just anyone; He is our Redeemer and Savior.
With the Resurrection and Ascension, Jesus will be leaving behind His humanity and going to the Father to become glorified. Jesus wants Mary to tell the disciples that He is returning to His Father and our Father, His God and our God. She delivers the message. How sad the disciples must have been when they heard this news.