KEY 1. ELDERSHIP (Acts 15-17,21-26)

The occasion for the first key to be used, then, came like this. As soon as Jesus had ascended to heaven Peter realised that a replacement had to be found for Judas. The apostolic number had to be restored.

So, "... in those days Peter stood up in the midst of the disciples (altogether the number of names was about a hundred and twenty), and said,
'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.

Therefore, of these men who have accompanied us all the time that the Lord Jesus went in and out among us, beginning from the baptism of John to that day when He was taken up from us, one of these must become a witness with us of His resurrection.
And they proposed two: Joseph called Barsabas, who was surnamed Justus, and Matthias.
And they prayed and said, 'You, O Lord, who know the hearts of all, show which of these two You have chosen to take part in this ministry and apostleship from which Judas by transgression fell, that he might go to his own place.'
And they cast their lots, and the lot fell on Matthias. And he was numbered with the eleven apostles," Acts 15-17,21-26.

Peter used Kingdom Key #1. He had opened the door to New Covenant Kingdom Eldership. It was the door into a new way of thinking, the Jesus' way, the way of the Word of the Kingdom.