Jews traditionally identify 613 commandments from God in the Torah, from the initial commands to Adam and Eve to “Be fruitful, and multiply, and replenish the earth, and subdue it”, through “Thou shalt not kill”, to the requirement that the congregation stone a blasphemer to death. No wonder that it is claimed that no one has ever been able to keep all 613 commandments!
When Jesus was asked which of the commandments was the most important he said “The first of all the commandments is, Hear, O Israel; The Lord our God is one Lord: And thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind, and with all thy strength: this is the first commandment. And the second is like, namely this, Thou shalt love thy neighbour as thyself. There is none other commandment greater than these.”
Because these two sound so much more forceful and defined than the Ten Commandments, people brought up in the Christian tradition assume they are Jesus’ original developments to monotheism.
Yet for the first one, Jesus is merely affirming his Jewishness. He is quoting the fundamental prayer of Judaism:
“Hear, O Israel: The Lord our God is one Lord: And thou shalt love the Lord thy God with all thine heart, and with all thy soul, and with all thy might. And these words, which I command thee this day, shall be in thine heart: And thou shalt teach them diligently unto thy children, and shalt talk of them when thou sittest in thine house, and when thou walkest by the way, and when thou liest down, and when thou risest up. And thou shalt bind them for a sign upon thine hand, and they shall be as frontlets between thine eyes. And thou shalt write them upon the posts of thine house, and upon thy gates.”
For its opening words, this is known as the Shema Yisrael (or just the Shema). It is the most important prayer, recited twice daily by observant Jews, taught to children to recite before sleep, attempted as the last words of the dying.
When you enter the home of an observant Jew you will notice a small container, a couple of inches long, fixed to the door frame. This is a mezuzah, containing the Shema.
For Jesus, as for any observant Jew, it was the single most important commandment from God.