But Thomas, one of the twelve, called [a]Didymus, was not with them when Jesus came. So the other disciples were saying to him, “We have seen the Lord!” But he said to them, “Unless I see in His hands the imprint of the nails, and put my finger into the place of the nails, and put my hand into His side, I will not believe.”
After eight days His disciples were again inside, and Thomas with them. Jesus *came, the doors having been shut, and stood in their midst and said, “Peace be with you.” Then He said to Thomas, “Reach here with your finger, and see My hands; and reach here your hand and put it into My side; and do not be unbelieving, but believing.” Thomas answered and said to Him, “My Lord and my God!” Jesus said to him, “Because you have seen Me, have you believed? Blessed are they who did not see, and yet believed.”
- John 20:24-29
He has always been remembered as "Doubting Thomas." But Thomas also believed.
Thomas was not mentioned again in the New Testament after the resurrection appearance of Jesus.
According to tradition, Thomas was sent to the Parthians, Medes, and Persians. Ultimately he reached India where he took the faith to the Malabar coast. There a large native population exists who call themselves the "Christians of St. Thomas."
Like all of the apostles, except for John, Thomas is believed to have died a martyr's death in 72. A.D.
The Catholic News Agency reports that Pope Benedict XVI had this to say about Thomas in 2006:
The Apostle Thomas’ case is important to us for at least three reasons. First, because it comforts us in our insecurity; second, because it shows us that every doubt can lead to an outcome brighter than any uncertainty; and, lastly, because the words that Jesus addressed to him remind us of the true meaning of mature faith and encourage us to persevere, despite the difficulty, along our journey of adhesion to him.