The notion that anything in the New Testament replaces anything in the Old is quite unintelligible. Likewise, the idea that Jesus left us – the church – with two commandments is a case of missing the point entirely. Matthew 22:37-40 (and Mark 12:29-31) deals with the question of which of the Commandments are the greatest, not which were left for the church to embrace. In fact, if this were about commandments (which it is not), then there would be simply one – Love (John 13:34; 15:12)! God supplies what God demands. To the point, Paul clues us in (Gal. 5:14), which has nothing to do with a commandment and everything to do with a single affection of the heart; not emotional, but purely logical. After a discourse on the irrational and irreligious (not to mention, theologically suicidal) notion of Christians adhering the Laws of Moses – to which he adds a rather graphic conclusion to such nonsense (Gal. 5:12) – Paul declares that the Law is fulfilled in (not replaced by) love.
The subject matter of Jesus’ discourse on this heading is not the commandments, but the love by which they are fulfilled. When God issued the commandments to the Israelites it was, then too, about love. The problem at hand for Israel was the fact that this love was precisely the unconditional and unmerited love of God, which outlet was only found in a shadowy set of commandments, ordinances, sacrifices, and simply mirrored in cultic worship. It was not until the Cross (and Resurrection) of Christ that the outlet for such love became widely accessible to all humanity. In Christ the two fulfill the others. Humanity needs only to live out of God’s perfect love, lavishing it on one another. In fact, this mutual lavishing of God’s perfect love on one another (“loving neighbor”) is the means to “loving God with all your faculties.” To be exact, it is God’s love for us collectively, which we accept individually and pour out corporately, by which we individually and corporately love God, thereby fulfilling all demands of the Law (which is not only written on stone, but on our hearts). There can never be a replacing of commandments (or all logic falls to the ground) and there can hardly be certain Mosaic Laws that are left for the church (which is highly irrational). It is love, however, which fulfills anything “old,” making it “new.”
The reason for the commandments was because of Law – the Law of Love, from the foundation of the earth. The Mosaic Laws were but a reflection of God’s original Laws – God’s worldview; God’s plans and purposes for creation – they are a reflection of who God is. Like the Natural Laws (i.e., for example, gravity) the Law of Love is older than humanity, let alone any commandments; for, it proceeds from the mind of God. The idea of “love” as a “law” does not concern a “command” but, rather, a foundational precept. God spoke creation into existence out of love, designed to express God-love within that creation. Love, having issued in a creative quality, is also experienced as a redemptive quality when humanity is healed by it. Loving God by loving neighbor is the work of God’s own love in creation. It is the image of God in us; the Law of Love at work in humanity, reconciling all things to God. The greatest commandments are fulfilled by love, and the Law of Love fills full (to overflowing) the image of God in creation.