And ye also shall bear witness. — The tense is present, and ye also bear witness; or, and ye also are witnesses. (Comp. Notes on Luke 24:48-49.) The Apostles themselves distinguished between their own witness of things which had come within their own experience and the witness borne by the power of the Holy Spirit, of which the Day of Pentecost was the first great instance. (Comp. Acts 5:32.)
Because ye have been with me from the beginning. — Comp. John 1:7; and Notes on Acts 1:21-22. The “beginning” of course means the beginning of the Messianic teaching and works of which they were to be witnesses.