15:1 Certain men "came down" from Judaea - direction is relative in the holy land. Jerusalem is the capitol of Judaea. It is the southern part of Israel. Paul and Barnabas were in Antioch, Syria, far north. Yet, wherever you are, you "go up" to Jerusalem. (vs 2).
1. There is a superior attitude there. Though it is the City of God, it is also the city of religious superiorty. Everyone there thinks they are right.
These "certain men" were probably believers, they were discussing salvation, however they were legalists.
They disputed hotly with Paul and Barnabas. They thought they should go back UP to Jerusalem for a council with the apostles and elders.
On the way there, they stopped in on the churches in Phenice and Samaria to report about the Gentiles being saved (these "certain men" were with them!)