What if Christians do love the Lord their God with all their heart, soul, mind, and strength? (Before you close this window with accusations of heresy, I encourage you to stick with me for a minute.)
Many of us know the conversation between Jesus and the Pharisee:
"'Teacher, which is the great commandment in the Law?' And [Jesus] said to him, 'You shall love the Lord your God with all your heart and with all your soul and with all your mind'" (Matthew 22:36-37).
Jesus is citing a famous Old Testament text: "Hear, O Israel: The LORD our God, the LORD is one. You shall love the LORD your God with all your heart and with all your soul and with all your might" (Deuteronomy 6:4-5).
But what is Jesus commanding with this "great commandment"?
Is Jesus Commanding A Perfect Love to God?
I've always thought that Jesus is talking about a perfect love for the Lord. This also is the only way I've heard it taught. In this view, he is citing this as the greatest commandment because a) we should strive to love God perfectly, and b) it's something only he can fulfill. In other words, we usually take Jesus' statement as saying that no one, except Christ himself, loves the Lord with all his heart, mind, soul, and strength, but that still is our goal.
In this way, as with many Old Testament laws, we take Jesus' statement as something a) we should seek to obey, and b) we must recognize we can't fully do and so we need Christ to fulfill it for us.
These points constitute right and good theology. I'd be an arrogant, deceived Christian if I tried to insinuate that I or any Christian can love the Lord their God with every part of them perfectly (which is how we read the "all").
But that's precisely what struck me, especially when reading through the Old Testament: Is the command from Deuteronomy talking about perfection? Is Jesus talking about perfection? Does "all" mean perfectly?
And I don't bring these questions up because I want to be 'different' or because of philosophical speculation; this question was thrown in my face while reading Deuteronomy 30...
A Surprising Connection in Deuteronomy 30
In Deuteronomy 30, Moses is talking about how in the far future, after years of Israel’s rebellion and exile, the Lord will gather his people once again. Most people take this as one of the first New Covenant promises, which I would agree: It sounds similar to other New Covenant promises, and Moses talks about a time when "the Lord you God will circumcise your heart...so that you will love the Lord...for the Lord will again take delight in prospering you..." (Deuteronomy 30:6-10). These are similar promises to New Covenant texts such as Jeremiah 32:37-41 and Ezekiel 36:22-32. Moreover, Paul himself says that in the New Covenant especially it is the circumcision of the heart which matters (Romans 2:28-29; Colossians 2:11).
So, Deuteronomy 30 is a New Covenant promise, fulfilled in the New Covenant come in Christ. But what does this have to do with the command to "love the Lord your God with all your heart, soul, mind, and strength"? Well, quite a lot.
Remember, it's earlier in Deuteronomy that this command to "love with all your heart, soul, mind, and strength" first occurs (Deuteronomy 6:5)—and Jesus quotes the command from Deuteronomy 6 in Matthew 22. But the "with all your heart and soul" command also is alluded to here in Deuteronomy 30 in this New Covenant paragraph—and twice! This is significant, especially since it is in the same book.
Look at the promises in Deuteronomy 30, especially the italicized parts of verses 6 and 10.
"...from there the LORD your God will gather you, and from there he will take you.  And the LORD your God will bring you into the land that your fathers possessed, that you may possess it. And he will make you more prosperous and numerous than your fathers.  And the LORD your God will circumcise your heart and the heart of your offspring, so that you will love the LORD your God with all your heart and with all your soul, that you may live.  And the LORD your God will put all these curses on your foes and enemies who persecuted you.  And you shall again obey the voice of the LORD and keep all his commandments that I command you today.  The LORD your God will make you abundantly prosperous in all the work of your hand, in the fruit of your womb and in the fruit of your cattle and in the fruit of your ground. For the LORD will again take delight in prospering you, as he took delight in your fathers,  when you obey the voice of the LORD your God, to keep his commandments and his statutes that are written in this Book of the Law, when you turn to the LORD your God with all your heart and with all your soul" (Deuteronomy 30:4-10).
Again, this seems to be a New Covenant promise and prophesy. The New Testament apostles saw this New Covenant as come in Christ. So what does this mean? Notice two important things from the above prargraph concerning the "all your heart and all your soul" idea.
First, and least important, in verse 10 it is said that in the New Covenant God's people will not only turn to him, but they will "turn to the Lord your God with all your heart and with all your soul." That's the first allusion to Deuteronomy 6. The turning (or 'repenting') in the New Covenant is will "all" the heart and "all" the soul. That's radical language.
But second, and more important, the allusion to Deuteronomy 6 is even clearer in verse 6. There Moses says, "The Lord your God will circumcise your heart..."—which remember has occurred for New Covenant believers (Romans 2:28-29; Colossians 2:11). But why? "...so that you will love the Lord your God with all your heart and with all your soul"!
In other words, part of the New Covenant promise isn't only that people have circumcised hearts, but they have circumcised hearts which make them love God with all their hearts and souls!
It seems, then, that Deuteronomy 30 states how the command from Deuteronomy 6 is fulfilled. (Remember once again, this takes place in the same book which the command originates.) The "all your heart and soul" comes in the New Covenant—which we're in!
A Pervasive Love
So here's the point: What if Jesus wasn't talking about perfection in his Greatest Commandment? Yes, God does deserve and require perfect love, that's true; we still need Christ's perfect obedience. But what if the command to love with "all" your heart, soul, mind, strength doesn't mean perfectly but pervasively? And moreover, what if Christians, because of their new heart, do love God like that? What if that is precisely what the new birth produces?
I know some of that sounds jarring, but it seems to me that is what is being talked about in Deuteronomy 30: In the New Covenant people will have circumcised hearts which allow them to love the Lord with "all" of them. And the apostles saw that this circumcision of heart was fulfilled in Christians in the New Testament church! If we think "all" means perfectly—which is how it's usually taught—then we've got a problem. But if "all" means genuinely, pervasively, in a new, radical way, then it fits. In this way, “love God with all your…” isn't talking about a perfect love. It's talking about a circumcision of the heart which results in a love for God which permeates all your heart, soul, mind, and strength.
The Wonder of the New Birth
The upshot then is that the new birth is a radical and wonderful reality. God takes someone who is a sinner through and through—someone who pervasively ("all"), with every part (“heart, soul, mind, strength”), is darkened and hates the light (John 3:19-20; Ephesians 4:18)—and changes them to someone who loves the Lord their God with "all" their heart, soul, mind, and strength!
This, in my opinion, with Deuteronomy 6 and 30 as our backdrop, is what Jesus was getting at. After all, he knew Deuteronomy well. It was the book he quoted in his temptation with Satan; it is the book where he cited his "Greatest Commandment." He certainly also knew that in Deuteronomy 30 it was promised that when the New Covenant came (which he was bringing!) a circumcision of heart would come which would grant what was commanded in Deuteronomy 6.
So, Christian—if you are a genuine, born-anew Christian—you do love God with all your heart, soul, mind, and strength. Yes, we must define "all." It does not mean a perfect love to God—we know that too well, we are not Christ! But it is a genuine, pervasive, total (meaning, in the total man) love. Because you have been circumcised in heart, you have a new heart "so that [you] love the Lord your God with all your heart and with all your soul" (Deuteronomy 30:6).
As Jesus asked Peter three times, "Do you love me?...Do you love me?...Do you love me?" (John 21:15-19), so the genuine Christian can say, "Yes, I—genuinely, pervasively, truly—do love you, Lord."
Being like that, having that changed heart, is the goal of the greatest commandment. "Grace be with all who love our Lord Jesus Christ with love incorruptible" (Ephesians 6:24). Let's be thankful for the new birth. Let's praise God for the new, God-given, God-loving heart.
I can anticipate a possible response to the above argumentation: Someone could say that the "all" does mean "perfectly"—that the New Covenant does have the goal of a perfect love to God, and that the New Covenant has begun—but that it has not come fully yet. In this argument, the promise of a circumcised heart "so as to love the Lord with all your heart and all your soul" is true and real, but not fully realized until the second coming of Christ.
In response to this, I would have at least two points (which can't be fully defended here), one concerning the New Covenant as a whole and another concerning Deuteronomy 30 specifically:
First, I see little evidence in the New Testament for a "here and not yet" New Covenant. There is a "here and not yet" eschatology, especially with the kingdom of God motif. But the New Covenant seems to be unequivocally here in Christ, in the church, in believers in Christ.
Second, in connection with this, in the promises of Deuteronomy 30 it seems bad exegesis to place such a large break between the "the Lord your God will circumcise your hearts" and (the next words) "so that you may love the Lord with all your heart and with all your soul." It is a flowing sentence and promise in Deuteronomy 30:6. So, when Paul says clearly the circumcision of the heart has come (which is prophesied in the New Covenant promise of Deuteronomy 30), we can assume it has that same effect as promised in Deuteronomy 30:6, namely, "so that [you] love the Lord your God with all your heart and all your soul."