“Brethren, it was needful that the Scripture should be fulfilled, which the Holy Spirit spoke before by the mouth of David concerning Judas, who was guide to them that took Jesus. For he was numbered among us, and received his portion in this ministry (diakonia).”
We see in these words clearly expressed Peter's high view of Scripture. It represented ‘words which the Holy Spirit spoke' and ‘must be fulfilled'. And it is clear that Peter had been meditating on the Scriptures and that they had brought home to him that there was a divine necessity with regard to Judas' betrayal (compare John 6:64). He had come to see that it came within the divine plan. He, who had once rebuked Jesus for contemplating suffering (Mark 8:32), had now been brought to see that experiencing the opposition of others to God was a part of what must be expected in His service, and that among the faithful would always be those who were not reliable.
It was in this sense that he saw the Scriptures that he had in mind as speaking of Judas. For Judas had truly been numbered among them and had received his share of the ministry, and yet it was he who had guided those who arrested Jesus to Him. He had been a man who had been greatly privileged, and he had fallen heavily. He was ever a lesson to us all that even the most favoured can fail (as Peter also had cause to know).