how many believers?

[theterminator]

15 In those days Peter stood up among the believers (a group numbering about a hundred and twenty) 16 and said, “Brothers and sisters,[a] the Scripture had to be fulfilled in which the Holy Spirit spoke long ago through David concerning Judas, who served as guide for those who arrested Jesus. 17 He was one of our number and shared in our ministry.”

does acts know of only 120 christian believers before the mass conversions at Pentecost?

[DCHindley]

15 In those days Peter stood up among the believers (a group numbering about a hundred and twenty) 16 and said, “Brothers and sisters,[a] the Scripture had to be fulfilled in which the Holy Spirit spoke long ago through David concerning Judas, who served as guide for those who arrested Jesus. 17 He was one of our number and shared in our ministry.”

does acts know of only 120 christian believers before the mass conversions at Pentecost?

I think all we can say for sure is that the Author of Acts wanted to portray that one group as numbering 120 individuals. The number of believers, in the author's eye, may have numbered more than 120, but he restricts that one meeting to 120 folks. For the time, that was a rather large group of persons to be meeting on one place.

Other questions to consider: Were they all men, or were wives and children present? If he had only men in mind, what about the status of wives and children associated with the men? What criteria was used by the author of Acts to define who qualifies as a "believer"?

We just don't know, and perhaps we just have to be content with that.

DCH

[Ben C. Smith]

15 In those days Peter stood up among the believers (a group numbering about a hundred and twenty) 16 and said, “Brothers and sisters,[a] the Scripture had to be fulfilled in which the Holy Spirit spoke long ago through David concerning Judas, who served as guide for those who arrested Jesus. 17 He was one of our number and shared in our ministry.”

does acts know of only 120 christian believers before the mass conversions at Pentecost?

The 120 are probably a symbolic number. From Mishnah 1.6:

And from where [do we derive] that a small [Sanhedrin] [comprises] twenty-three [judges]? As it says, (Numbers 35:24-25) "the assembly shall judge... the assembly shall deliver." The assembly judges and the assembly delivers- behold [the number of judges adds to] twenty. From where [do we derive] that the assembly is ten? As it says, (Numbers 14:27) "Until when shall I bear this wicked assembly." This excludes Joshua and Caleb. And from where [do we derive that we] add three more? This is implied by the [verse], as it says, (Exodus 23:2) "Do not follow the many to do evil." Should I learn to follow them to do good? If so, why does it say (Exodus 23:2) "Following the many to distort [justice]" - your following to do good is not like your following to do evil. Following to do good [i.e. acquittal] is by one, following to do evil [i.e. conviction] is by two. Since a court cannot [contain an] even [number of members], we add [to the number of judges] one more - behold this is twenty-three. And how many [inhabitants] must a city have before it may have a Sanhedrin? One hundred and twenty. Rabbi Nechemiah says, two hundred and thirty, [each judge] corresponding to a chief of a group of ten.

So perhaps the church, with 120 members, was considered large enough to merit the body of apostles set over it. Additionally, perhaps the notion is that there was one chief/judge (that is, one apostle) for every group of 10 in the early church. From 1QS (the Community Rule):

Wherever there be ten men who have formally enrolled in the community, one who is a priest is not to depart from them. When they sit in his presence, they are to take their places according to their respective ranks; and the same order is to obtain when they meet for common counsel.

When they set the table for a meal or prepare wine to drink, the priest is first to put forth his hand to invoke a blessing on the first portion of the bread and wine.

In any place where there happen to be ten such men, there is not to be absent from them one who will be available at all times, day and night, to interpret the Law (Torah), each of them doing so in turn.

Luke 22.30 specifies that there was one apostle/disciple for each of the 12 tribes of Israel.

Ben.

[Huon]

With 30 persons in 70 CE, there could be 120 persons around 100-110 CE...

[Huon]

Ben, you are speaking of the Essenes.
I think that there is a difference in numbers between the Essenes and the followers of James, Peter and Paul, during the first century.

Even a small group of believers has a local leader, but that does not need an important organisation.
And that local leader is not necessarily accepted by another different group.

[Ben C. Smith]

Ben, you are speaking of the Essenes.
I think that there is a difference in numbers between the Essenes and the followers of James, Peter and Paul, during the first century.

Even a small group of believers has a local leader, but that does not need an important organisation.
And that local leader is not necessarily accepted by another different group.

I quoted both from a Qumran scroll and from the Mishnah. More than just Essenes are in view here.