V. The address of St. Peter led the Apostles to practical action. He laid the basis of it in the book of Psalms, the mystical application of which to our Lord and His sufferings he recognises, selecting passages from the sixty-ninth and the one hundred and ninth Psalms as depicting the sin and the fate of Judas Iscariot;[41] and then sets forth the necessity of filling up the vacancy in the apostolic office, a fact of which he had doubtless been certified by the Master Himself. He speaks as if the College of the Apostles had a definite work and office; a witness peculiar to themselves as Apostles, which no others except Apostles could render. This is manifest from the language of St. Peter. He lays down the conditions of a possible Apostle: he must have been a witness of all that Jesus had done and taught from the time of His baptism to His ascension. But this qualification alone would not make a man an Apostle, or qualify him to bear the witness peculiar to the apostolic office. There were evidently numerous such witnesses, but they were not Apostles, and had none of the power and privileges of the Twelve. He must be chosen by his brother Apostles, and their choice must be endorsed by Heaven; and then the chosen witness, who had known the past, could testify to the resurrection in particular, with a weight, authority, and dignity he never possessed before. The apostolic office was the germ out of which the whole Christian ministry was developed, and the apostolic witness was typical of that witness to the resurrection which is not the duty alone, but also the strength and glory of the Christian ministry; for it is only as the ministers and witnesses of a risen and glorified Christ that they differ from the officials of a purely human association.[42] [41] Peter may have learned this mystical mode of interpretation from our Lord Himself in His conversations. See Luke xxiv. 44-9.