The lot fell upon Matthias, and he was numbered with the eleven apostles - Acts of the Apostles, chapter 1, verse 26.

“He needed to be a witness not of the times before or after that event, and not of the signs and wonders, but only of the Resurrection itself. For the rest happened by general admission, openly but the Resurrection took place secretly, and was known to these men only” - Saint John Chrysostom.