Church Fathers on John 20:19

The disciples, when they heard what Mary told them, were obliged either to disbelieve, or, if they believed, to grieve that He did not count them worthy to have the sight of Him. He did not let them however pass a whole day in such reflections, but in the midst of their longing trembling desires to see Him, presented Himself to them: Then the same day at evening, being the first day of the week, when the doors were shut where the disciples were assembled for fear of the Jews.

Wherein is strewn the infirmity of the Apostles. They assembled with doors shut, through that same fear of the Jews, which had before scattered them: Came Jesus, and stood in the midst. He came in the evening, because they would be the most afraid at that time.

and with shut doors, that he might show how that in the very same way he had risen again, i.e. with the stone lying on the sepulcher.