Mt 22:34-40
34When the Pharisees heard that [Jesus] had silenced the Sadducees, they gathered together, 35and one of them [a scholar of the law] tested him by asking, 36“Teacher, which commandment in the law is the greatest?” 37He said to him, “You shall love the Lord, your God, with all your heart, with all your soul, and with all your mind. 38This is the greatest and the first commandment. 39The second is like it: You shall love your neighbor as yourself. 40The whole law and the prophets depend on these two commandments.”
The Greatest Commandment: The Pharisees who are learned in the Torah (the first five books of the Bible) have identified 613 commandments in it—248 positive (“thou shalt”) and 365 negative (“thou shalt not”). Obviously, no one can remember them all, and not all commandments are of the same weight. The Pharisees themselves distinguish the “heavy” (serious) from the “light.” The “Ten Command ments” are heavy ones. An example of a “light” command ment would be not plowing with an ox or an ass harnessed together (Dt 22:11).
Others would try to sum up the Torah’s commandments in a small number of precepts or a summary statement. David proposed eleven (Ps 15), Isaiah six (33:15), Micah three (6:8). Amos simply says: “Seek the Lord” (5:4). Tobit gives a parting advice: “Serve God faithfully and do what is right before him” (14:9).
In reply to a Pharisee’s question about the “greatest commandment,” Jesus cites Dt 6:5, the Shemah-prayer (“Hear, O Israel”) which the Jews recite daily. This is the basic principle of the Mosaic Law. Since the Lord alone is God, all must love him with an undivided heart. Jesus, however, attaches to it the second commandment, equal in importance, citing Lv 19:18: “You shall love your neighbor as yourself.” And by “neighbor,” Jesus means not just a fellow Israelite, but anyone, especially when the person is in need (see Lk 10:29-33, the parable of the Good Samaritan).
Elsewhere, Jesus gives another summary of the Torah: “Do to others whatever you would have them do to you. This is the law and the prophets” (Mt 7:12). The believers, in turn, echo Jesus in summarizing the Law. Paul writes: “Owe nothing to anyone, except to love one another; for the one who loves another has fulfilled the law” (Rom 13:8).