3 Now there would be no great merit and glorious blessedness in believing, if the Lord had always appeared in His Risen Body to the eyes of men. The Holy Ghost then has brought this great gift to them that should believe, that Him whom they should not see with the eyes of flesh, they might with a mind sobered from carnal desires, and inebriated with spiritual longings, sigh after. Whence it was that when that disciple who had said that he would not believe, unless he touched with the hands His Scars, after he had handled the Lord's Body, cried out as though awaking from sleep, “My Lord and my God;” the Lord said to him, “Because you have seen Me, you have believed; blessed are they that have not seen, and yet have believed.” This blessedness has the Holy Ghost, the Comforter, brought to us, that the form of a servant which He took from the Virgin's womb, being removed from the eyes of flesh, the purified eye of the mind might be directed to This Form of God, in which He continued equal with the Father, even when He vouchsafed to appear in the Flesh; so as that with the Same Spirit filled the Apostle might say, “Though we have known Christ after the flesh; yet now we know Him so no longer.” Because even the Flesh of Christ he knew not after the flesh, but after the Spirit, who, not by touching in curiosity, but in believing assured, acknowledges the power of His Resurrection; not saying in his heart, “Who has ascended into heaven? That is, to bring Christ down; or, Who has descended into the deep? That is, to bring back Christ from the dead.” “But,” says he, “the word is near you, in your mouth, that Jesus is the Lord; and if you shall believe in your heart that God has raised Him from the dead, you shall be saved. For with the heart man believes unto righteousness, and with the mouth confession is made unto salvation.” These, Brethren, are the words of the Apostle, pouring them forth with the holy inebriation of the Holy Ghost Himself.
Source: Sermons on Selected Lessons of the New Testament (New Advent)