Do not be bound together with unbelievers; for what partnership have righteousness and lawlessness, or what fellowship has light with darkness? (2 Corinthians 6:14)
Paul’s exhortation to the Corinthians is one of the greatest challenges facing believers today. In a world bombarding us with temptation, God’s people need to keep clear the spiritual lines of demarcation, both for the sake of the gospel and our own testimonies. As John MacArthur explains in his sermon “Separating from Unbelievers, Part 1,” Paul’s words mean “we cannot overindulge ourselves in their world to the detriment of our testimony within the body of Christ.”
Highlighting the inherent conflict between believers and sinners, John says:
The pure and the polluted share nothing in common ultimately. And the people of God cannot form intimate relationships with those who don’t belong to God. All relationships like that are superficial. You cannot make a meaningful relationship with an enemy of the gospel. They live in a different world with a different and completely hostile and antagonistic leader.
That does not mean we are to cut off all contact with the world—that’s hardly feasible. And even if it were, such isolation would violate the Lord’s instruction to go into the world and make disciples (Matthew 28:19). But Scripture is likewise clear that we need to avoid the lawlessness and darkness of this corrupt world.
As we approach the conclusion of our series on what it means to be in the world but not of it, we need to consider separation from the world and how it can enhance or hinder the progress of the gospel and the development of our individual testimonies.
In the context of 2 Corinthians 6:14-7:1, Paul is discussing the purity of the church, and rebuking those who had attempted to blend God’s truth with paganism. Religious syncretism was rampant in the first-century world, and the New Testament church was not immune to its influence. From the founding of the church, false teachers immediately married God’s truth to elements of pagan culture and practice.
And while the paganism of today looks different than that of Paul’s day, Satan’s agenda has not changed at all. In his sermon “Separating from Unbelievers, Part 2,” John MacArthur explains how our enemy still seeks to gain a foothold in the church:
It’s very much like modern Christianity today, by the way, that seeks to blend Christianity with popular culture, wants to make Christianity more popular, less different, more palatable, less offensive, less narrow, less exclusive. And the result of it is that true Christianity and the purity of God’s Word gets corrupted by compromise, and the church can become useless and shameful and blasphemous in mocking the truth.
Throughout Scripture, the Lord consistently makes clear His command to keep His people pure from worldly influences and blasphemous corruption. Paul’s exhortation expanded on commands God had issued to Israel through the prophet Isaiah: “‘Therefore, come out from their midst and be separate,’ says the Lord, ‘and do not touch what is unclean’” (2 Corinthians 6:17).
In his commentary on 2 Corinthians, John MacArthur explains the urgency behind Paul’s exhortation:
To be bound together with unbelievers is not only foolish and irreverent, but it also disobeys God’s explicit command, expressed in the two imperative verbs translated “come out” and “be separate.” “Therefore” links the command in this verse with the principle expressed in verse 16. As those personally indwelt by the living God, believers are to avoid any joint spiritual effort with unbelievers. As the temple of the living God, they must not be linked for the cause of the advancement of divine truth with any form of false religion.
The thought in this verse hearkens back to Isaiah 52, where God commanded His people, “Depart, depart, go out from there, touch nothing unclean; go out of the midst of her, purify yourselves, you who carry the vessels of the Lord” (Isaiah 52:11). Christians, like Israel at the time of her salvation (Isaiah 52:7-10), must make a clean break with all false religion to avoid its contaminating influence (cf. 2 Timothy 2:16-17). . . .
It has always been God’s will for His people to be distinct from unbelievers. In Leviticus 20:24, 26 God said to Israel, “I am the Lord your God, who has separated you from the peoples. . . . Thus you are to be holy to Me, for I the Lord am holy; and I have set you apart from the peoples to be Mine.” In the New Testament Peter reiterated that principle, exhorting believers, “As obedient children, do not be conformed to the former lusts which were yours in your ignorance, but like the Holy One who called you, be holy yourselves also in all your behavior; because it is written, ‘You shall be holy, for I am holy’” (1 Peter 1:14-16).  John MacArthur, The MacArthur New Testament Commentary: 2 Corinthians (Chicago: Moody Press, 2003) 254-255.
The church cannot be an effective lighthouse for the truth if it insists on cloaking itself in the trappings of worldliness and ecumenical capitulation. For the sake of our worship, evangelism, and spiritual stability, we need to reject the corrupting influence of the world and protect the purity of God’s people.
But if Paul’s words about being unequally yoked with unbelievers are directed at the church, how does the principle apply to individuals? If the prohibitions of 2 Corinthians 6 are directed to the church, how do we determine the appropriate level of interaction—if any—with the world on a personal level?
In his commentary on a parallel passage (Hebrews 13:10-13), John MacArthur explains that the need for separation from the world is not merely a matter of physical proximity:
Separation from the system does not mean separation from unbelievers in the sense of never having contact with them. If this were so, we could never witness to them or be hospitable to them. Nor does it mean we try to escape the world by becoming monastics. As far as separation is concerned, the world is an attitude, an orientation, not a place. As long as we are in the flesh, we take some of the world with us wherever we go. Paradoxically, a holier-than-thou attitude is the essence of worldliness, because it is centered in pride. It is worldly attitudes and habits from which we are to separate ourselves. And we can participate in many worldly things just as easily with Christians as with non-Christians.
In His high priestly prayer, Jesus describes our proper relationship to the world. “I do not ask Thee to take them out of the world, but to keep them from the evil one. They are not of the world, even as I am not of the world. Sanctify them in the truth; Thy word is truth. As Thou didst send Me into the world, I also have sent them into the world” (John 17:15-18). God sends us into the physical world, the world where people live. What we are to be separate from is the world system, the way the world’s people live (cf. 1 John 2:15-17).
You do not have to participate actively in the system to be a part of it. It is just as worldly to want to do the things of the world as to do them.  John MacArthur, The MacArthur New Testament Commentary: Hebrews (Chicago: Moody Press, 1983) 442.
In that sense, the degree to which you are of the world is not measured merely by your contact with it, but by how much it has taken up residence and influence in your heart. You might not outwardly display a love for the trends and tastes of the world, but a haughty attitude is no less worldly.
As believers, we need to guard ourselves from the kind of relationships that will entangle us with the world’s system. But just as important, we need to guard our hearts from following the prideful, selfish lead of this worldly, sinful culture. And we need to remember that God has sent us into the world for the work of the gospel, and that we must keep ourselves unstained by the world (James 1:27) if we’re going to fulfill that work.