What is the Insider Movement that is sweeping across some Christian circles? Is it Biblically sound?
Everyone has someone to whom they’re closer to than others. Someone they can share things with that they wouldn’t tell others. Some scholars believe that James, John, and Peter were closer to Jesus than the other disciples. They were insiders, so to speak. Jesus showed them things that He didn’t show the others, so having someone close to you or being close to someone you know is not bad in itself, but when this becomes part of a Christian movement, then it’s a good idea to look into it. Jesus had a closer relationship with James, Peter, and John, as we see when He went to heal Jairus’ daughter, but “he allowed no one to follow him except Peter and James and John the brother of James” (Mark 5:37), and at the Mount of Transfiguration, “Jesus took with him Peter and James, and John his brother, and led them up a high mountain by themselves” (Matt 17:1), so again, having an intimate relationship with someone, especially with Christ, is not bad, but what about the Insider Movement? We receive lots of questions from our Contact Us link and this movement is beginning to get some attention, so let’s examine what the Insider Movement is, and why it’s better to know about it ahead of time than to be caught off guard. 
The definition of an insider movement is not necessarily religious, but it’s defined as a group or a network of people, but they’re from a non-Christian religion. Even though they’d tell you they’re not Christian’s, they still consider themselves as followers of Jesus, but they follow Him while living within their own culture and within the local traditions or customs. They might even consider themselves part of the universal body of Christ. Some Insider Movements are composed of Jews, Muslims and Hindus. Some even claim they can rely on Jesus Christ for their salvation, and yet remain within the culture and customs of the locations where they live at. Some will cite the Apostle Paul’s letter to the Corinthians where he wrote, “To the Jews I became as a Jew, in order to win Jews. To those under the law I became as one under the law (though not being myself under the law) that I might win those under the law. To those outside the law I became as one outside the law (not being outside the law of God but under the law of Christ) that I might win those outside the law” (1 Cor 9:20-21), but Paul is not teaching that we should “Christianize” our neighborhood. The context of this verse is to preach the gospel, not change the world. Of course it’s good to do good when we can, especially when we see evil or the weak and poor exploited, but Paul says, “I have become all things to all people, that by all means I might save some” (1 Cor 9:22b), not that I might integrate the culture into his religion to become an insider.
Some Christian missionaries, of all people, were apparently the ones who begin the Insider Movement, whether they realized it or not. When the missionaries began to enter into lands where the Islamic faith  dominated, they wanted the Christian faith to be somewhat blended in with the local culture and customs. Of course, these would vary in different parts of the world, but some missionaries winked at mixing the Islamic faith with Jesus. They condoned it by their silence, so many Muslims who know Jesus continue to pray and go to mosque, observe Ramadan, adhere to strict dietary laws, and even study the Quran, and are not warned by the missionaries that Jesus is the one and only way (Acts 4:12), and worshiping God must be in spirit and in truth (John 4:24), but also they have to understand that it’s a lifetime commitment, because we seek Him above all things (Matt 6:33). Most believers know that we cannot participate in any other religion that is contrary to the Word of God. For example, the Quran teaches that Jesus Christ was only a Prophet. We know that He is much more than that. He is God! Similar experiences have been allowed for Jewish “converts,” but they also don’t believe what the Bible teaches about Jesus Christ. Clearly, God will not accept this worship.
Come out of Her
The Insider Movement might change the culture, but does it change the heart? Only the Holy Spirit can do that. And besides, we are frequently told to come out of this world. Jesus said the disciples “are not of the world, just as I am not of the world” (John 17:16). James asked, “Do you not know that friendship with the world is enmity with God? Therefore whoever wishes to be a friend of the world makes himself an enemy of God” (James 4:4). The Apostle John writes, “Do not love the world or the things in the world. If anyone loves the world, the love of the Father is not in him” (1 John 2:15). This doesn’t mean we hate the world or hate the people in the world, but we hate the things the world represents, and that is the pride of life, the lust of the eyes, and the lust of the flesh (Gen 3:6; 1 John 2:16). The same three things that caused mankind’s fall from grace and barred mankind from the Garden.
When Lot and his family were rescued from Sodom, shortly before its destruction, Lot’s wife looked back and became a pillar of salt. She was told to not look back, but she did it anyway…perhaps out of regret for what she left behind. Lot and his family left Sodom, but Sodom never left them. If you read the last few accounts from Lot’s life, he lived in a cave because he lived in fear the rest of his life, and was duped into committing sexual immorality with his own daughters (Gen 19:30-38). It says, “Thus both the daughters of Lot became pregnant by their father. The firstborn bore a son and called his name Moab. He is the father of the Moabites to this day. The younger also bore a son and called his name Ben-ammi. He is the father of the Ammonites to this day” (Gen 19:36-38). The Moabites and Ammonites would turn out to be a thorn in Israel’s side, and be so for hundreds of years. The lesson is, try to be a force for good in the world, but not by being part of the world. That’s the danger of the Insider Movement. It’s trying to “Christianize” the local village but not “Christianize” the people. That doesn’t work. That doesn’t convert people. It takes the preaching of the Word and the Spirit of God to quicken people to eternal life (Eph 2:1-4). It’s sort of an insider-work though…when the Spirit of God creates a child of God, and it’s always for the glory of God. That’s all that matters (Psalm 115:1).
Here is some related reading for you: How Can You Bring Someone Out of a Cult? 
Resource – Scripture quotations are from The Holy Bible, English Standard Version® (ESV®), Crossway Bibles. (2007). ESV: Study Bible : English standard version. Wheaton, Ill: Crossway Bibles. Used by permission. All rights reserved.