“While we were in conference we were infiltrated by spies pretending to be Christians, who slipped in to find out just how free true Christians are. … We didn’t give them the time of day”. 

Gal 2:4, 5 EHP 

Wherever there is progress, success or happiness, there is often trouble of some sort lurking close by. It is true that “Satan never sleeps”. 
The conflict with Judaism was the big issue in the New Testament. Some of the new Christians had been Jews – born and bred – until a short while before Pentecost. But in most of the Jewish synagogues there were people who had been born Gentiles but had become Jews by conversion. (These were sometimes termed “proselytes”). When Christianity came along a number of these Gentile converts to Judaism now converted to Christianity. Then there were Gentiles who had converted “straight” to Christianity without first becoming Jewish in faith. Some times the old Jewish elements tried to cause trouble in the church because they did not want to see their Gentile converts go. Sometimes they just made trouble for the church because they thought it was Judaism gone wrong. There were many conflicting and confusing elements in and around the church and Satan was bent on using them to stop the spread of the Good News of Jesus Christ. In this Jerusalem meeting opponents of Paul’s ideas sneaked in to the meeting and created trouble, no doubt trying to drive a wedge between Paul and the other apostles. Paul was perceptive enough to recognize them for what they were and strong enough to persuade the conference to have nothing to do with them. 
Beware of troublemakers of all varieties. They are still as active as ever. Deal with them strongly and quickly. 

Lord, help me to spot and root out troublemakers