If the Lord Jesus Christ had not literally risen physically from the grave, we could never be certain that he had ever really finished the work...if he has died for our sins, we must not only be certain that he has died, but that he has finished dying, and that there is no longer death...when God raised his Son from the dead, he was proclaiming to the whole world...he has done everything. He has fulfilled every demand. Here he is risen-therefore I am satisfied with him...

The devil cannot hold him; death and hell cannot hold him. He has mastered them all, he has emerged on the other side. He is the Son of God, and he has completed the work which the Father had sent him to do....It is only in the light of the Resurrection that I finally have an assurance of my sins forgiven. It is only in the light of the Resurrection that I ultimately know that I stand in the presence of God absolved from guilt and shame and every condemnation.

If it is not a fact that Christ literally rose from the grave, then you are still guilty before God. Your punishment has not been borne, your sins have not been dealt with, you are yet in your sins. It matters that much: without the Resurrection you have no standing at all.

Adrian Warnock, Raised with Christ, Crossway, Wheaton, Il, 2010 quoting Martyn Lloyd-Jones, The Assurance of Our Salvation (Wheaton, Il, Crossway, 2000) 492