The command to love is old in that it existed and was known before Christ’s coming. In its simplest form it is found in Leviticus 19:18, which says: “Thou shalt love thy neighbor as thyself: I am the LORD.” This is the verse to which Jesus referred when He was asked His opinion regarding the first and greatest commandment. He said that the greatest commandment was that recorded in Deuteronomy 6:5: “Thou shalt love the LORD thy God with all thine heart, and with all thy soul, and with all thy might.” But the second, he said, was Leviticus 19:18.
In what sense, then, is the command to love a new commandment? It is new in that it was raised to an entirely new emphasis and level by the teaching and example of Jesus. William Barclay suggests two ways in which this is true, to which we may also add a third.
First, in Jesus love became new in “the extent to which it reached.” In Christ’s day love was not new, but at the same time there were few who would consider love to be an obligation beyond a fairly limited circle of close friends or, at the widest extent, one’s nation. To the orthodox Jew the sinner was not to be loved. Rather, he was one whom God obviously wished to destroy. Nor were Gentiles to be loved. They were created by God for hell. By contrast Jesus extended His love to everybody. He became the “friend of sinners,” a sympathetic listener and teacher of women (who were also despised), and eventually the one through whom the salvation of God was extended even to the Gentile world. His last words to His disciples were that they were to make disciples “of all nations” (Matt. 28:19) and that they were to be His witnesses “in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth” (Acts 1:8).
Second, in Jesus love became new in “the lengths to which it would go.” Here one must look to the cross, for it is at the cross that the height and depth of God’s love is seen, as it is not seen to the same degree elsewhere. To what length will the love of God go? To the length at which the very Son of God will take upon Himself a human form, die on a cross, and there bear the sin of a fallen race, so that in bearing the punishment for that sin He is actually alienated for a time from God the Father and thus cries out in deep agony, “My God, my God, why hast thou forsaken me?” (Mark 15:34). That is the extent to which the love of God goes. It is thus that love becomes an entirely new thing in Christ.
Third, in Jesus love is made new in the degree to which it is realized. John indicates this by adding in verse 8, “which thing is true in him and in you, because the darkness is past, and the true light now shineth.” In this verse “true” (alethes, alethinos) means “genuine,” and the point is that the true or genuine love, like genuine righteousness, is now being seen not only in Jesus but in those who are made alive in Him as well. In this sense, what was not possible under the Old Testament dispensation is now possible; for the life of Jesus, which expresses itself in love, is in His people.