Beginning (arxameno). Aorist middle participle of arcw, agreeing (nominative) with o kurio Ihsou (the Lord Jesus). The ministry of Jesus began with the ministry of John. Strictly speaking arxameno should be the accusative and agree with martura (witness) in verse 1 Timothy 22 , but the construction is a bit free. The ministry of Jesus began with the baptism of John and lasted until the Ascension. A witness with us of his resurrection (martura th anastasew autou sun hmin). This Peter considers the essential thing in a successor to Judas. The one chosen should be a personal witness who can speak from his own experience of the ministry, resurrection, and ascension of the Lord Jesus. One can easily see that this qualification will soon put an end to those who bear such personal testimony.