In those days Peter stood up among the brothers (the company of persons was in all about 120) and said, “Brothers, the Scripture had to be fulfilled, which the Holy Spirit spoke beforehand by the mouth of David concerning Judas, who became a guide to those who arrested Jesus. For he was numbered among us and was allotted his share in this ministry.” (Now this man acquired a field with the reward of his wickedness, and falling headlong he burst open in the middle and all his bowels gushed out. And it became known to all the inhabitants of Jerusalem, so that the field was called in their own language Akeldama, that is, Field of Blood.) “For it is written in the Book of Psalms, “‘May his camp become desolate, and let there be no one to dwell in it’; and “‘Let another take his office.’ So one of the men who have accompanied us during all the time that the Lord Jesus went in and out among us, beginning from the baptism of John until the day when he was taken up from us—one of these men must become with us a witness to his resurrection.” And they put forward two, Joseph called Barsabbas, who was also called Justus, and Matthias. And they prayed and said, “You, Lord, who know the hearts of all, show which one of these two you have chosen to take the place in this ministry and apostleship from which Judas turned aside to go to his own place.” And they cast lots for them, and the lot fell on Matthias, and he was numbered with the eleven apostles. (Act 1:15-26)
120 believers is how many the church started out with. A person wonders if they were all gathered together at once in this upper room or if they were scattered throughout the city. It’s not a very large number, but it seems it would crowd any dining room. It would also draw quite a bit of attention. Perhaps they were gathered together for a service of prayer. Peter wants to replace Judas and restore the number of apostles to 12.
There is actually a difference between apostle and disciple. We here about the 12 disciples, these later become apostles. Disciple means student or follower. Jesus had many more than 12, but he had 12 who were special to him, 12 whom he planned to give apostleship. The word apostle is the nouning of a verb, when you apostle someone you send them. In Jesus day people would contract apostles. These would be men you sent to speak on your behalf with your authority. It would be something like giving a person power of attorney today. The problem is that Judas offed himself. We get two versions of how this happened. Matthew says he hanged himself, and Luke tells us he fell in a field and exploded more or less. I think commentaries and people make more out of this than is necessary. Saying that this is a discrepancy that is irreconcilable. Either way it was a bad death. Personally, growing up and reading these I always figured he fell and exploded when they cut him down from the rope. Seems to me a guy hanging for a few days in the son might have bloated enough that that would happen. Like a dead cow in the pasture. Others have thought me trite for such an explanation. I don’t really care, Judas is dead. Hung himself could be just an expression for the curse he brought upon him too. But he is out of the picture, and Peter wants a new man to take the apostleship.
Twelve was an important number in Israel. It shows up here and there in scripture. The Church would be the new Israel and Israel had had 12 tribes, named after 12 brothers. Now there would be a new Israel and so again 12 stems from which Israel would grow. Of course, the qualifications for this particular apostleship would soon die out and would not allow for renewal. The term is used for others, such as Paul, and Paul even talks about others such as James the brother of Jesus as being an apostle. But you have to wonder about all that. He was an apostle if Paul calls him such, but he could not have been one who shared in this same apostleship that Peter is here talking about. For one thing, he is in the upper room, and is passed over as one who does not meet the qualifications for this apostleship that Peter lays out. He did not accompany Jesus from the time of his baptism by John in the wilderness. In fact, the gospels show absolute unbelief on behalf of Jesus brothers up until the crucifixion. In John chapter 7 they even try to kill Jesus themselves! Presumably he had witnessed the resurrection and he was a man. He would die a horrible death being beaten to death by men with fuller’s clubs. But he does not meet the qualifications spelled out. (Neither do any of the so called Quorum of the 12 of the LDS, whatever they are, they are not a continuation of this 12)
But what does all that mean? Why did Peter think it necessary to have 12 at that time, but then they never get replaced, and there seem to be more than 12 later. Why is that of these 12, so few contribute to the New Testament most of which was written by one not counted in this 12? I can only say that it had to do with Pentecost and the rebirth of the church on that day. That the Holy Spirit would light on 12 with tongues of flame as a symbol to all who would gather to hear them of what is happening, the rebirth of Israel. That perhaps 12 needed to be selected beforehand so that they themselves would understand this that was happening. After Pentecost there would be room for others to be called apostles. There apostleship would not be lessened by not being among these twelve. These twelve indeed would testify to their apostleship as we see with Paul and Peter. Peter even suffers correction from Paul without questioning Paul as an upstart. But on the day of Pentecost there would be twelve flames and this would not wait for Paul’s conversion, nor would it go to James or any other brother of Jesus simply because of relation by blood. The lot would fall on Matthias.