Acts 1:21

Wherefore of these men which have companied with us. — From the retrospective glance at the guilt and punishment of the traitor, Peter passes, as with a practical sagacity, to the one thing that was now needful for the work of the infant Church. They, the Apostles, must present themselves to the people in their symbolic completeness, as sent to the twelve tribes of Israel, and the gap left by the traitor must be filled by one qualified, as they were, to bear witness of what had been said or done by their Lord during His ministry, and, above all, of His resurrection from the dead. That would seem, even in St. Paul’s estimate, to have been a condition of apostleship (1 Corinthians 9:1).

Went in and out... — The phrase was a familiar Hebrew phrase for the whole of a man’s life and conduct. (Comp. Acts 9:28.)