4 For, though one of the chosen and holy twelve, yet he was an Israelite, of the Lord's nation, that Thomas who desired to put his fingers into the places of the wounds. The Lord censured him just as He did this ruler. To the ruler He said, “Unless you see signs and wonders, you believe not;” and to Thomas He said, “Because you have seen, you have believed.” He had come to the Galileans after the Samaritans, who had believed His word, before whom He wrought no miracles, whom He without anxiety quickly left, strong in faith, because by the presence of His divinity He had not left them.
Now, then, when the Lord said to Thomas, “Come, reach hither your hand, and be not faithless, but believing;” and he, having touched the places of the wounds, exclaimed, and said, “My Lord, and my God;” he is chided, and has it said to him, “Because you have seen, you have believed.” Why, but “because a prophet has no honor in his own country?” But since this Prophet has honor among strangers, what follows? “Blessed are they that have not seen, and yet have believed.” We are the persons here foretold; and that which the Lord by anticipation praised, He has deigned to fulfill even in us.
They saw Him, who crucified Him, and touched Him with their hands, and thus a few believed; we have not seen nor handled Him, we have heard and believed. May it be our lot, that the blessedness which He has promised may be made good in us: both here, because we have been preferred to His own country; and in the world to come, because we have been grafted in instead of the branches that were broken off!
Source: Tractates on the Gospel of John (New Advent)