In the Epistle to the Galatians, written by the Apostle Paul to a number of early Christian communities in the Roman province of Galatia in central Anatolia, he wrote: "Bear one another's burdens, and so fulfill the law of Christ.". This phrase appears once and is never defined. It has been suggested that "the law of Christ" could be an allusion to the second greatest commandment or the New Commandment. Others suggest this phrase is just another name for "the law of God" as Christians believe the Messiah is God. Possibly related, in a letter to the early Christians of Corinth, Greece, in the First Epistle to the Corinthians, Paul wrote: "To those not having the law I became like one not having the law, so as to win those not having the law.". In the Greek, the wording is, "to those without law, as without law -- -- that I might gain those without law." It is not clear exactly what Paul means by the phrase, "the law of Christ". Although Paul mentions Biblical law several times and preached about Ten Commandment topics such as idolatry, he consistently denies that salvation, or justification before God, is based on "works of the law", though the meaning of this phrase is also disputed by scholars, see for example the New Perspective on Paul#Works of the Law.
Many Christians believe that the Sermon on the Mount is a form of commentary on the Ten Commandments. It portrays Christ as the true interpreter of the Mosaic Law. In the Expounding of the Law, Jesus said that he did not come to abolish the law or the prophets, but to fulfill them. Jesus explicitly warns of severe concequence to those who break and teach others to break one of the least of the commands of God In the apocryphal Gospel of Marcion's version of Luke 23:2 we find the extension: "We found this fellow perverting the nation and destroying the law and the prophets". While the New Testament records several unique sayings of Jesus that may be described as "commandments," it only records one that he explicitly identified as such. This is the New Commandment of that the disciples should love one another as he himself had loved them. These commandments are commonly seen as a basis of Christian ethics.
uses the phrases of "royal law" and "law of liberty" in reference to the Second greatest commandment, part of :
Theological interpretations
In his Summa Theologiae I-II qq. 106-109, a section of the Summa known as the Treatise on Law, Saint Thomas Aquinas discusses the Law of Christ as the "New Law". He argues that it was virtually contained in the Old Law, that is the Old Testament, as a seed but only brought to perfection by Jesus Christ who perfectly fulfilled it. The ends of the Old and New are one and the same, being subjection to God's order, but they are different in that the New Law makes attaining the end possible. Meanwhile, since all law ultimately has reference to Divine Reason governing all things, the New Law contains and helps the human being fulfill the Natural Law which prescribes acts of virtue. Thus, Aquinas defines the New Law as "chiefly the grace itself of the Holy Ghost, which is given to those who believe in Christ, " but adds that it also "contains certain things that dispose us to receive the grace of the Holy Ghost, and pertaining to the use of that grace." Therefore,"the New Law is in the first place a law that is inscribed on our hearts, but that secondarily it is a written law". The Catholic theologianBernhard Häring presents the Law of Christ as Christ himself in his person because Jesus was able to fulfill the law and provide us with the effect of this fulfillment. The Evangelical theologian Douglas J. Moo argues that "the law of Christ" is strongly connected to the Mosaic Law, for example that nine of the Ten Commandments are included. George R. Law argues that the New Covenant is the Law of Christ, and that the details are expressed in the Sermon on the Mount.
