The collect for today, the Feast Day of St Thomas, from the 1662 Book of Common Prayer:

Almighty and everliving God, who for the more confirmation of the faith didst suffer thy holy Apostle Thomas to be doubtful in thy Son's resurrection; Grant us so perfectly, and without all doubt, to believe in thy Son Jesus Christ, that our faith in thy sight may never be reproved. Hear us, O Lord, through the same Jesus Christ, to whom, with thee and the Holy Ghost, be all honour and glory, now and for evermore. Amen.

The Epistle: Ephesians 2:19-22
The Gospel: St John 20:24-31

More on St Thomas here.

Click for larger viewArtwork: Andrea del Verrocchio, Christ and Saint Thomas (The Incredulity of Saint Thomas), 1467-83, Bronze, Orsanmichele, Florence.