“Therefore, from among the men who have accompanied us during the whole time the Lord Jesus went in and out among us— beginning from the baptism of John until the day He was taken up from us—from among these, it is necessary that one become a witness with us of His resurrection.”
So they proposed two: Joseph, called Barsabbas, who was also known as Justus, and Matthias. Then they prayed, “You, Lord, know the hearts of all; show which of these two You have chosen to take the place in this apostolic service that Judas left to go to his own place.” Then they cast lots for them, and the lot fell to Matthias. So he was numbered with the 11 apostles.
Acts 1:21-26 (HCSB)