Acts 10:45 kjv
45. And they of the circumcision which believed were astonished, as many as came with Peter, because that on the Gentiles also was poured out the gift of the Holy Ghost.
When I read (of the circumcision) I automatically think of circumcision party / judaizer faction
en.m.wikipedia.org
Acts 15:5 kjv
5. But there rose up certain of the sect of the Pharisees which believed, saying, That it was needful to circumcise them, and to command
them to keep the law of Moses.
Of course we leap to
Our Galatians passage again
Galatians 1:6 kjv
6. I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel:
And, the other gospel is that the Gentiles could not be saved by grace alone, but had to keep also the law of Moses.
Maybe reading the Wikipedia link will help.
eddif