Although the church at Pergamos had been preaching the Gospel, while holding fast to the name of Jesus and had not denied the faith, even under the pressure of risking their lives, Jesus said they had among themselves those who held to the doctrine of Balaam (Revelation 2:14)! What does this mean? Who was Balaam, and what was his doctrine?
Balaam was an Old Testament figure. He was a prophet who made great claims about his faith and doctrine (Numbers 22:18, 38; 24:3-4, 15-16). He is a strange figure to say the least, but, whatever else we may say about the man, the text does say he spoke with God, and God spoke with him (Numbers 22:20-21). Yet, at the end of the day, we can conclude that he didn’t have a heart for God’s word. Instead, he showed himself opposed to the word, which God gave him to speak. Rather, he was greedy for the wealth offered him by Balac, the enemy of God’s people. Balac wanted Balaam to curse Israel, in order to allow Moab to be successful in battle against them. So, instead of working to establish the will of God, Balaam worked against the will of God to establish the desires of Balac, because Balaam lusted after the reward, which Balac offered him, if he would do as the king wanted.
How can we put this in the context of what was going on in Pergamos? According to Numbers 31:16, it was Balaam’s plan to corrupt Israel by getting God’s people to worship another god. The prophet presumed that, if he was able to do that, God would be forced to judge them and perhaps even abandon his people for breaking covenant with him.
Moab worshiped Baal-Peor, which simply means they worshiped Baal on Mt. Peor in Moab. The book of Numbers records how Israel abandoned their covenant with Yahweh by becoming “joined” with Baal-Peor (Numbers 25:3). Their covenant with the Lord was likened to a marriage covenant (cf. Jeremiah 3:14), so by joining oneself to a god of the surrounding nations was likened to an adulterous wife rejecting God to be married to or at least have an affair with another god (cf. Malachi 2: 11). With this in mind, it seems that there were some at Pergamos who encouraged the brethren to sin more and more, because not only were they not under the Law, but in doing so grace would abound to them more and more (Romans 3:8).
Perhaps the idea was that, if one would worship in the pagan temples he or she could use the Gospel to draw pagans away from their gods in order to embrace Jesus as their Messiah. Gentile believers, more so than Messianic Jews, might be susceptible to this kind of teaching. One could even support such an argument by saying: “hadn’t Paul gone to the synagogues in order to gain a Jewish following? Therefore, gentiles should do the same in the context of gaining believers from the pagan temples.”
We need to keep in mind that there were spies among believers in the first century AD. That is, not everyone who worshiped with believers and worked with them were true believers in Christ (Acts 5:1-13; cf. 2Corinthians 11:26; Galatians 2:4). Jesus had warned his disciples that this sort of thing would take place (cf. Matthew 13:24-28). Moreover, these enemies were not to be removed from the body of disciples, lest some of Christ’s own people would be rooted up with them. Rather, they were permitted to remain with the true believers in Jesus until the time of the harvest. The harvest would come at the end of the then present age, or at the coming of Christ (Matthew 13:28-30; cf. 13:36-43 and 24:29-31).
We can conclude from this, therefore, that there were men at Pergamos who, for all intents and purposes, seemed to be prophets of God, yet their hearts were sold out for gain. They were enemies of the Gospel, who were planted in the church in Pergamos by the person or group of people behind the persecution that had erupted all over Asia (cp. 1Peter 1:1, 6-7). There are only two individuals in the Empire who had power enough to do such a thing. The first was Caesar, who might have worked through the authorities in Asia who represented him. However, we can eliminate Rome as the persecutor for two reasons. First, before Nero, no emperor persecuted Christians, and even the persecution begun by Nero was a local persecution that erupted over the blame for the fire at Rome. It did not spread to the rest of the empire. Secondly, Rome can be eliminated here in Pergamos, as the persecutor of Christians, because Rome didn’t seek to remove their enemies by planting spies among them. They simply arrested them and killed whomsoever they wished.
The Second person who could be behind the persecution in Asia was the high priest at Jerusalem. He had tremendous influence with all Jews, wherever they could be found. If this is logically sound, then Annas, the high priest who had so much influence in the crucifixion of Jesus, can be shown to be the one behind the persecution referred to by Jesus in Revelation 2 & 3. The plan may have been to show how gentile believers weren’t believers at all, and needed to be circumcised, i.e. obey the Law, in order to be saved.
 They were spies sent into the church by the man behind the persecution in Asia.
 Note that in Peter’s fist epistle we are told persecution had erupted in five different Roman provinces in Asia Minor (1Peter 1:1, 6-7). It is easier to believe such a thing had a single cause rather than many reasons for the persecution developing simultaneously without a master mind behind them.