St Thomas Apostle
In the Mass of St Thomas, the liturgy reminds us that the Apostles are the foundation of the Church of which Christ is the chief corner-stone (Epistle); that is why their feasts were formerly kept like Sundays.
The Gospel relates the famous scene which occurred in the Upper Room after the Lord's Resurrection. St Thomas doubted: and it was only when Jesus made him put his finger into His wounds that, passing suddenly from incredulity to ardent faith, he exclaimed: "My Lord and my God." That finger, says a Father of the Church, has become the master of the world because it showed him the reality of the flesh of Jesus Christ. Let us therefore believe in the great mystery of an Incarnate Word which will soon be manifested to the world. - The name of St Thomas occurs in the Canon of the Mass (first list).
The elevation at Mass having been instituted as a reply to the heresy of Berengarius who denied the real presence, let us contemplate in a spirit of faith the sacred elements when they are raised and say with St Thomas: "My Lord and my God," a practice enriched by Pope St Pius X with an indulgence of seven years and seven quarantines, and a plenary indulgence once a week on the ordinary conditions. - The double elevation recalls the real separation of Our Lord's Body and Blood on the Cross.
At that time, Thomas, one of the twelve, who is called Didymus, was not with them when Jesus came. The other disciples therefore said to him, We have seen the Lord. But he said to them, Except I shall see in His hands the print of the nails, and put my hand into His side, I will not believe. And after eight days, again His disciples were within, and Thomas wth them. Jesus cometh, the doors being shut and stood in the midst, and said, Peace be to you. Then He saith to Thomas, "Put in thy finger hither, and see My hands, and bring hither thy hand, and put it into My side; and be not faithless but believing."Thomas answered, and said to Him, My Lord and my God. Jesus saith to him, " Because Thou hast seen Me, Thomas, thou hast believed: blessed are they that have not seen, and have believed."
(St John 20:24-29)
Source of picture: Master of Ehningen Altars, Stuttgart, 1476. See also https://www.pinterest.co.uk/pin/323062973242783829/