Wherefore of these men - Of those who had witnessed the life and works of Christ, and who were therefore qualified to discharge the duties of the office from which Judas fell. Probably Peter refers to the seventy disciples, Luke 10:1-2.
Went in and out - A phrase signifying that he was their constant companion. It expresses in general all the actions of the life, Psalms 121:8; Deuteronomy 28:19; Deuteronomy 31:2.