Luke
Acts 15:5BSB·traditional attribution

But some believers from the party of the Pharisees stood up and declared, “The Gentiles must be circumcised and required to obey the law of Moses.”

John Calvin Reformed @genevareformer

5. Certain of the sect of the Pharisees. It is not without cause that Luke expresseth what kind of men they were which went about to trouble or hinder Paul, even at Jerusalem also. And it is to be thought that the evil flowed from that fountain; and that Luke doth now more plainly express, that there brake out now also fans [disturbers] out of...

Matthew Henry Presbyterian @wholebiblehenry

Even when things go on very smoothly and pleasantly in a state or in a church, it is folly to be secure, and to think the mountain stands strong and cannot be moved; some uneasiness or other will arise, which is not foreseen, cannot be prevented, but must be prepared for.

Commenting on Acts 15:1-5

John Gill Reformed Baptist @doctorgill

But there rose up certain of the sect of the Pharisees,.... Which was the strictest sect of religion among the Jews: which believed; that Jesus was the Messiah, and professed their faith in him, and were members of the church, though they still retained many of their pharisaical tenets, and are therefore said to be of that sect: these rose up in opposition to Paul...