Charles Ellicott Commentary Acts 1:21

"Of the men therefore that have companied with us all the time that the Lord Jesus went in and went out among us," — Acts 1:21 (ASV)

Wherefore of these men which have companied with us.—From the retrospective glance at the guilt and punishment of the traitor, Peter passes, with practical sagacity, to the one thing that was now necessary 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 to what their Lord had said or done during His ministry and, above all, to His resurrection from the dead. This, it would seem, even in St. Paul’s estimation, was a condition of apostleship (1 Corinthians 9:1).

Went in and out . . .—This phrase was a familiar Hebrew phrase for the whole of a person’s life and conduct .