Let us put Jesus in historic context first. Judaism at that point in time was roughly 500 years old. The best independent, anthropological record we have of that religion dates from about 525 B.C.E. (Before Common Era) give or take 25 years. One of the most common understanding of the Jewish teachings dates from approximately 30 B.C.E. It comes from Hillel a Doctor of Law roughly before the time of Jesus.
When a heathen who wished to become a Jew asked him for a summary of the Jewish religion in the most concise terms, Hillel said: "What is hateful to thee, do not unto thy fellow man: this is the whole Law; the rest is mere commentary" (Shab. 31a).