Many Christians are afraid of refugees from Islamic nations and want to exclude them to keep their nation Christian. This is an Old Testament attitude.
In the Old Testament, the people had to separate themselves from evil influences, because they had no spiritual protection. That is why they had to expel the Canaanites from the Promised Land. God did not want his people to pick up the evil spirits that they carried. That changed with the cross, because the cross and resurrection of Jesus destroyed the powers of evil. This spiritual protection means that evil cannot touch his people.
This change is reflected in the attitude to lepers. In the Old Testament, people kept separate from lepers because if they touched them, the evil spirits which had harmed them might cross over and hurt them too. Jesus took the opposite approach, he touched the lepers and healed them. He knew that any evil spirits attacking the leper, could not touch him. He knew the power of the Holy Spirit that was upon him could restore the leper.
The same applies to the nations of the world. In the Old Testament age, God’s people had to keep separate from the nations, because they might corrupt them by opening them to evil spirits. Following the cross, Christians are to go into the world and make disciples of the nations. The spiritual protection provided by the cross keeps them safe from evil spirits. The power of the Holy Spirits upon them means that they will transform the nations, rather than the nations being transformed by them.
The same applies to Islamic refugees moving into so-called Christian nations. Prior to the cross, we would have had to kept separate. In the New Testament age, we have spiritual protection from any evil spirits they are carrying. More important, the power of the Spirit that is available to the church is so strong, that the refugees should be overwhelmed by his influence.
If the power of the Spirit on the churches in Europe is so weak that it cannot draw a few refugees into the gospel, then it is already dead. The refugees are just exposing its real state.