John 20:24

But Thomas, one of the twelve, called Didymus, was not with them when Jesus came.

Thomas' absence was a tragic loss to him; and what was true of him is true of all Christians in a spiritual sense. He was absent from the assembly, and thus he failed to see the Lord and receive his blessing. That absence contributed to his delinquency in his refusal to believe that anything had really happened in his absence. Absence from Christian worship quickly moves a believer into a posture of doubt and unbelief. "Didymus" means "twin" (English Revised Version, margin).