By Mike Flom
One passage of Scripture (of many) I have mulled over for some time is 1 Thes. 3:12-13:
“And may the Lord make you increase and abound in love for one another and all [men] . . . so that he may establish your hearts blameless in holiness before our God and Father, at the coming of our Lord Jesus Christ with all his saints.”
What does love have to do with holiness?
It seems that in this passage the apostle Paul is directly connecting love for our fellow men with our own personal holiness or sanctification. More than that, the conjunction “so that” suggests that love is a prerequisite or a basis for holiness. But when I think of holiness, I usually think more along the lines of moral purity. In fact, a few verses later in the same epistle, Paul writes “This is the will of God, your sanctification: that you abstain from sexual immorality” (4:3). So, are we limiting our understanding of holiness too much if we confine it to moral purity, or is holiness more expansive? More to the point, what does holiness have to do with love?
By the way, this is not the only passage in the New Testament that indicates a direct connection with love and holiness. John Piper in his internet series of lab commentaries on Ephesians also cites Ephesians 1:4-5 (especially as translated in NKJV) and Philippians 1:9-10. In both passages, as with the one from I Thessalonians above, love is connected with our being presented holy (or pure) before God.
The word holy, as R.C. Sproul says, has the same two meanings applied to people as when it is applied to God: (1) to be set apart or different; and (2) to be morally pure. We are saints (holy ones) who are separated to God for His use but also who are “called to be saints”; that is, we are called to be separated from the world in the sense of not conforming to its ways and conduct (1 Cor.1:2; Rom. 12:2). We are called to be holy as He is holy (Lev. 19:2; 1 Pet. 1:16). Of course, we cannot be holy exactly as God is, because we are not like Him in His incommunicable traits such omniscience and omnipotence, but we can be like Him –to a certain degree- in His communicable traits, especially love, since God is love (1 John 4:8, 16).
Now, back to the connection between holiness and love. Keeping in mind the idea of the separateness aspect of holiness, another commentary led me to one explanation that gets to the heart of the matter. It is found in Jesus’ words to His disciples in the Sermon on the Mount and in the Gospel of John concerning love.
First, with regard to loving one another, Jesus tells us in John 13:34-35:
“A new commandment I give to you, that you love one another: just as I have loved you, you also are to love one another. By this all people will know that you are my disciples, if you have love for one another.”
Jesus is saying that love for one another is a distinguishing mark of Christians. It is so distinctive that it will set us apart from the world. Although Jesus words here apply to the entire body of Christ, practically speaking, loving each other goes on in a local church. How wonderful it is to be a part of a body of believers (as I am) who really do care for each other, and how unique it must be for an unbeliever used to a world characterized by selfishness, division, and exclusion, to witness this love in a body of believers. This kind of brotherly love reflects the way Jesus loves us and is evangelistic. It is holy - different from the world’s love.
Secondly, Jesus also spoke of a love we should have for all men, especially our enemies. In the Sermon on the Mount He said,
“You have heard that it was said, ‘You shall love your neighbor and hate your enemy’. But I say to you, Love your enemies and pray for those who persecute you, so that you may be sons of your Father who is in heaven. . . . For if you love those who love you, what reward do you have? Do not even the tax collectors do the same? . . . Do not even the Gentiles do the same? You therefore must be perfect even as your heavenly Father is perfect.” (Matt. 5:43-48)
Notice the separation Jesus speaks of here. Our love for others should exceed loving only those who love us which is typical of the world; our love should extend to our enemies as well. In this way, we will be acting like the sons of God we are, imitating God in loving our enemies. God loves His enemies all over the world every day by giving them sunshine and rain for food and gladness (Matt. 5:45, Acts 14:17). Jesus, on the cross, prayed for His enemies when He said, “Father, forgive them for what they do” (Luke 23:34). Also, speaking of enemies, before we were saved, we too were God’s enemies, but He loved us so much He did not even spare in his own Son Jesus to die for us and reconcile us to Him (Rom. 5:10, 8:32; Col.1:21-22).
After exhorting us to love our enemies in verse 48 of Matt. 5 above, Jesus said “Be perfect even as your heavenly Father is perfect.” He could have said “Be holy for I am holy.” Love for our enemies distinguishes us from the world and this love is also holy.
Loving one another and loving all people – even our enemies – differentiates us from the way of the world and from the way we used to live before God saved us.
In this way we are holy. Therefore, we can say that love truly is the basis for holiness, or as John Piper says, “Love is the form that holiness takes in relation to others.” 
Loving people is hard, though, even if they are not our enemies, so we must pursue love just as we are to pursue holiness (I Cor. 14:1; Heb. 12:14); and we can pray for increasing love for others just as Paul prayed for the Thessalonians in the opening passage.
 Sproul, R.C., The Holiness of God, (Wheaton, IL, Tyndale House, 1998), 157  Piper, John, Providence, (Wheaton, IL, Crossway, 2021), 600