When the Pharisees heard that Jesus had silenced the Sadducees,
they gathered together, and one of them,
a scholar of the law tested him by asking,
“Teacher, which commandment in the law is the greatest?”
He said to him,
“You shall love the Lord, your God,
with all your heart,
with all your soul,
and with all your mind.
This is the greatest and the first commandment.
The second is like it:
You shall love your neighbor as yourself.
The whole law and the prophets depend on these two commandments.”
Matthew 22: 34-40
The first commandment recited by Christ is taken from the Shema, the prayer recited by the Jews morning and night. All his Jewish listeners would have known it by heart and His choice of it should have been unsurprising to his interlocutors. They would also have not been surprised by his addition of a second commandment which required loving your neighbor as yourself. The commandment is taken from Leviticus 19: 18. The great Rabbi Hillel, who died when Christ was a child, stated the commandment negatively: What is hateful to you, do not do to your fellow: this is the whole Torah; the rest is the explanation; go and learn. Saint Paul, who doubtless was quite familiar with the teachings of Hillel, echoed this teaching: For all the law is fulfilled in one word, even in this; Thou shalt love thy neighbor as thyself. Galatians 5: 14.
If the answers of Christ were fairly obvious, why was the question asked? Probably to test His knowledge. Did this small town carpenter know the teaching of Hillel? Perhaps to find fodder to accuse Him of heresy. Whatever was the motivation, Christ yet again revealed Himself as completely supportive of the heart of the Jewish Law. Normally Christ opposed it only in regard to the Jewish ritual purity laws, at least as they had been interpreted. Where he differed with a Jewish teaching outside of ritual purity, normally He increased the severity of the Law, forbidding divorce for example, or proclaiming that a man who looked lustfully at a woman was guilty of adultery. Christ would add to the Jewish law and shore it up, but He came not to do away with it, but rather to perfect it.
“Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.”
Matthew 5: 17