Imagine if you were reading a book about a cat to your children. Page 1 says that the cat sat on a hat. Page 2 then says that the cat ate the hat. Then you get to Page 3 and it does not use the word "cat," but describes a four legged creature playing with an ant. One child speaks up and says, that sounds like an aardvark. Aardvarks are associated with ants. So the child concludes that the creature on Page 3 is an aardvark. You keep reading and see on Page 4 that the cat sits on a mat. On Page 5 the cat takes a nap.
The problem with the child's interpretation is that the book is about a cat, not an aardvark. To interpret that creature on Page 3 as an aardvark is nonsensical. It is essentially arguing that even though the entire book is about a cat, the author suddenly talks about an aardvark and then goes back to talking about a cat.
To put it plainly, it is to argue that the book is about X here, X here, X here, and X here, but a passage within the book is suddenly talking about Y that has nothing to do with X.
It is like reading Moby Dick and thinking that a passage about the "creature" against which Ahab has a vendetta is suddenly about a giant squid. The entire book is about a white whale. It is absurd to take it out of context because "creature" has a familiar ring to those who have read 20,000 Leagues under the Sea.
Yet, there are two interpretations on the table. What is to decide between them if not the context? What often happens is that one interpretation wants to emphasize the context of the literary argument of a book, and the other wants to de-emphasize it in order to emphasize the context of his own argument and tradition. This is often the case when one reads that Christ commands His followers to love their enemies, and to give to those who do not necessarily love them.
It is simply taken for granted that the reader knows what Christ means when He argues that one should "love his enemies." The phrase is most commonly interpreted to mean, "love the unbeliever." The problem with this interpretation, as popular as it is, is that it ignores the context of the three passages in which it appears: Matthew 5, Luke 6, and Romans 12.
When I bring this fact up to most evangelicals, they just don't seem to care much. I think this may be somewhat due to their lack of interpreting texts in context as a practice. They simply are not use to reading Matthew or Luke or Romans as a literary work that is making a coherent argument.
Despite this deficiency, however, I want to attempt to communicate this idea here.
We'll start with Matthew. Matthew sets up his Gospel to address the Jewish-Gentile conflict within the church. He utilizes Christ's earthly teaching in such a way that he applies it to this conflict. Hence, he creates an inclusio with Christ's teaching that addresses how one treats fellow members within the covenant community.
In Matthew 5, He argues that the law has not been appropriately applied to one's practices if it does not love others in the covenant, whether one's brother with whom there is a disagreement, one's spouse, one to whom a promise has been made, etc. He finally applies the law of loving to not only one who the Jews consider their fellow Jews, but also to those with whom they are in conflict in the covenant community. The rabbinic tradition had taught that one was to love his friends but could hate his enemies. In the Jewish-Gentile conflict, Gentiles, even though they had become Christians, were considered the enemy. They were the Jews oppressors. The strong resentment that they felt toward Gentiles did not disappear once the Gentiles became Christians. In fact, many of the parables Jesus tells later in Matthew indicate that there was a lot of animosity on the part of the Jews for God even including Gentiles as equals in the kingdom. They wanted nothing to do with them, a common report we see throughout the New Testament.
Matthew ends his inclusio of Christ's teaching in Matthew 25, where it is also clear that Christ is concerned with whether someone who claims to be one of His followers evidences that by taking care of "one of the least of these brothers of Mine" who represent Christ Himself.
The middle of Christ's teaching in Matthew is filled with teachings about forgiving fellow believers, loving God and other members of the covenant as that which contains all of the law, and parables that let us in on the conflict that is going on between Jewish and Gentile Christians. There is also a large section that contains Christ's rejection of unbelieving Jews that communicates the idea that Jewish Christians should now identify themselves primarily as believers in Christ, and not as primarily Jews who need to separate themselves from Gentile believers, since those unbelieving Jews have rejected the Messiah. They, thus, have more of a connection with their fellow Gentile believers, because of their connection to Christ, than they do with the unbelieving Jews who became the murderers of Christ and the persecutors of the Jewish disciples. He even ends the teaching about His parousia by warning Christians that Christ will severely judge those who mistreat their "fellow servants."
What this helps us see is that the entirety of Matthew's message is about how one group of believers treat another group of believers, who they see as those who are their enemies, i.e., Gentiles. This is why Matthew starts his Gospel off with Gentile Magi and not poor shepherds, as in Luke.
So here is the problem with interpreting the enemy passages as unbelieving enemies. It essentially wants to argue that these texts are complete digressions that have nothing to do with the immediate context or the larger literary arguments of these books. It essentially argues that the book is about X, but this text is about Y that does not contribute at all to the argument of X.
Luke is very similar to Matthew in that Luke is also arguing about Christian brothers, but in Luke's case, he is talking to Christians who have wealth and power. His warning, from start to finish, is about how one treats fellow Christians who are in need. His entire argument, like Matthew's, is internally covenantal. It simply has nothing to do with how one helps unbelievers. Again, this misses the point. When Luke deals with one's enemies, he doesn't use the word "enemy/opponent," but instead describes one who does not love them. It is important to understand that love is often seen in terms of one who does good by giving to another, and hate is seen in one who does not give. Luke presents Jesus as saying that there is a visible community of believers and some will love and some will hate, some will give and some will withhold what is needed from other believers. Jesus simply teaches that His true followers within the community will give to other members of the covenant community. They will be the ones who love other believers in their giving, even when not loved by those other believers. Again, Luke's entire argument has to do with believers helping other believers, even if those other believers are not one's loving friends. The rebuke is that even unbelievers give to those who love them among them, but Christians are to give to other Christians, even when those other Christians have not shown the same love toward them.
Again, to argue that Luke is talking about Christians giving to unbelievers is to argue that Luke is about X, but this text is a digression that teaches Y that has nothing to do with X.
Finally, Romans is about the Jewish-Gentile conflict again. The Jewish Christians are having major issues with the Gentile Christians, and vice versa. Paul lays out that salvation is for both Jew and Gentile through faith, both become true Israel, and thus, both groups should see one another as one in Christ. Hence, Chapters 12 and 13 begins the conclusion of Paul's argument. It tells Christians that they are one body in Christ, and should therefore treat one another lovingly and in seeking one another's repentance in doing good to one another. In Chapters 14 and 15, he continues his argument that they should not judge one another for how they use created things like wine and holy days, etc.
Now, to make the idea that one is to love his enemies in Romans 12 and 13 about unbelievers ignores all of this. The opponent the Roman Christians are being called to love is one another. That is clear in the context of the book and the immediate context.
Again, to argue otherwise, is to say that the entire book is about X, but this text is a digression that talks about Y that has nothing to do with X.
It essentially argues that the entire book is about a cat, but here it is about an aardvark. Yet, it is the context that decides between interpretations. It gets to say what it is about, regardless of what it sounds like to the reader, who often replaces the context of the literary argument with their own context and tradition. But if it's a cat on page 1, and a cat on page 2, and a cat on page 4 and 5, then it's a cat on page 3, and to argue otherwise is to lose any objective sense on what a particular text was meant to convey in terms of authorial intent.
These texts are about internal covenant problems, problems within the church, where believers are told to love other believers, even if those other believers do not love them, even if those other believers are among the Gentile oppressors, one's enemies, even if those other believers do wrong to them. That is Christ's teaching. And why are they to do this? Because other believers represent Christ within the covenant community, and as representatives, they are to display Christ's forgiveness toward one another, Christ's love toward one another, because this displays the gospel to everyone who sees it.
Believers are sinners who are one another's enemies, who hate one another, but are brought together in Christ's love and forgiveness to be united to one another as they are to Christ. That is the context of these passages, and when we ignore it, we ignore what Christ has truly commanded His people to do, which, as John puts it, to "love one another as I have loved you."