John Chrysostom — as excerpted in the Catena Aurea on John 20:26-31

“(Hom. lxxxvii) Consider the mercy of the Lord, how for the sake of one soul, He exhibits His wounds. And yet the disciples deserved credit, and He had Himself foretold the event. Notwithstanding, because one person, Thomas, would examine Him, Christ allowed him. But He did not appear to him immediately, but waited till the eighth day, in order that the admonition being given in the presence of the disciples, might kindle in him greater desire, and strengthen his faith for the future. And after eight days again His disciples were within, and Thomas with them: then came Jesus, the doors being shut, and stood in the midst, and said, Peace be unto you.”