Thomas
First appears at Matthew 10:3
First named in Scripture at Matthew 10:3 — read the chapter.
What Thomas Did
The apostle called Didymus, the Twin: when Jesus would return to Judea where the Jews sought to stone Him, Thomas rallied the rest; in the upper room his question drew the words "I am the way, the truth, and the life"; absent at the first appearance of the risen Lord, he demanded the print of the nails — and eight days later made the highest confession in the Gospels.
Accomplished for Good
"Let us also go, that we may die with him" (John 11:16) — a loyalty deeper than his doubts; and at last, seeing the wounds: "My Lord and my God" (John 20:28).
Mistakes and Failures
"Except I shall see in his hands the print of the nails, and put my finger into the print of the nails, and thrust my hand into his side, I will not believe" (John 20:25) — a week of unbelief while the church rejoiced, from the condition he set on believing.
From Easton’s Bible Dictionary (1897)
twin, one of the twelve (Matthew 10:3; Mark 3:18, etc.). He was also called Didymus (John 11:16; 20:24), which is the Greek equivalent of the Hebrew name. All we know regarding him is recorded in the fourth Gospel (John 11:15, 16; 14:4, 5; 20:24, 25, 26-29). Prom the circumstance that in the lists of the apostles he is always mentioned along with Matthew, who was the son of Alphaeus (Mark 3:18), and that these two are always followed by James, who was also the son of Alphaeus, it has been supposed that these three, Matthew, Thomas, and James, were brothers.