Albert Barnes Commentary Acts 15:5

"But there rose up certain of the sect of the Pharisees who believed, saying, It is needful to circumcise them, and to charge them to keep the law of Moses." — Acts 15:5 (ASV)

But there rose up, etc. It has been doubted whether these are the words of Paul and Barnabas, relating what occurred at Antioch, or whether they are the words of Luke, recording what took place in Jerusalem. The correct interpretation is probably that which refers it to the latter. For:

1. This seems to be the most obvious interpretation.
2. The use of the words "rose up" implies that. Those who disturbed the church at Antioch are said to have come down from Judea (Acts 15:1), and if this passage referred to that occurrence, the same words would have been retained.
3. The particular specification here of "the sect of the Pharisees," suggests that this was an occurrence taking place in Jerusalem. No such specification exists regarding those who came down to Antioch; but it seems here that this party in Jerusalem still resolved to abide by the law, and to impose those rites on the Christian converts. However, this interpretation is by no means certain.

Which believed. Who maintained, or taught.

That it was needful, etc. Refer to Barnes on Acts 15:1.