If you put “light” and “darkness” in the same room, what would they have in common? Could they find a level of fellowship that they could enjoy? If you put “righteousness” and “lawlessness” in the same room, what would they have in common? Could they establish a partnership 
together? If you put Christ and Satan in the same room, what would they have in common? Could they come to a harmonious agreement about living together? If you put “the temple of God” and “idols” in the same room, what would they have in common? Could they find a way to both be acceptably worshiped by Christians?
The subjects in each of these questions could not be more diametrically opposed to one another! But each question is asked in a Biblical context that first instructs, “Do not be unequally yoked together with unbelievers,” and then asks, “What has a believer in common with an unbeliever?” (2 Cor. 6:14-17). Does God have anything to say about a Christian entering a serious relationship with a non-Christian? Go back and read the questions in the first paragraph.