Acts 1:16-17 "Men and brethren, this Scripture had to be fulfilled, which the Holy Spirit spoke before by the mouth of David concerning Judas, who became a guide to those who arrested Jesus; for he was numbered with us and obtained a part in this ministry."
Acts 1:20 "For it is written in the Book of Psalms: 'Let his dwelling place be desolate, And let no one live in it'; and, 'Let another take his office.'
It is interesting that Jesus didn't send the Holy Spirit to empower the disciples right away. Instead He had them wait, together, and begin their walk purely from obedience. They clustered together and turned to the Lord in prayer, as their primary pursuit. It's also interesting to consider the subject of Peter's first sermon. It wasn't a grand presentation of the Gospel or even a recounting of the amazing events of Jesus' death, resurrection and ascension. The first message he gave explained the actions of the traitor, Judas, and provided directions to replace him. You can imagine the identify crisis that Judas' actions might have caused among the remaining disciples. After all, he had been one of them for the full three years. If he was capable of such evil, they may have wondered if they also would fail the Lord. I doubt that they expected the demise of Jesus to come from their midst. They needed to be healed and restored before they could minister to others. Peter finds the answers in the Book of Psalms. He quotes verses from three different Psalms (41:9, 69:25 and 109:8) to show that the person and actions of Judas and were foretold centuries before. He also found the directions for replacing Judas there. Peter demonstrated for us the role of scripture in understanding the dilemmas of life and finding the directions for living ("How do I understand my problems?" and "What shall I do now?"). And we see the integrity and relevance of scripture as the Holy Spirit began to speak through His words before He showed up to baptize them at Pentecost in a more dramatic scene. And so the church began with this huddled group of about 120 followers who were beginning to follow a path of prayer, study of God's Word and mutual encouragement. Before we can minister we also need to be healed and restored and we find great encouragement when surrounded with believers in a context of prayer and the study of God's Word.