2 Corinthians 6v14-15
Do not be unequally yoked with unbelievers. For what partnership has righteousness with lawlessness? Or what fellowship has light with darkness? What accord has Christ with Belial? Or what portion does a believer share with an unbeliever?

This is an important truth laid out by Paul and it is important for us to understand it. Yoked implies to be interweaved or allied with unbelievers through actions. This does not mean for us to stay away from the unbeliever, remember Jesus came for the sick, the hurting, and the lost. But rather we are to set ourselves apart by acting as Christ out of reverence to Christ not out of holier than thou self righteousness so that we may minister to the change that has overwhelmed our lives to those lost. We are to spread the power of Christ to all people at all cost but to live as those partnered with Christ and not this world.