There is a story among the Jews about a man who wanted to learn the entire Torah (the Law) while standing on one foot. He inquired of one rabbi, who chased him away with a stick. Finally he went to the rabbi Hillel, who told him, “What is hateful to you, do not do to your neighbor; this is the whole Torah. The rest is commentary. Now go and study.”
Whether or not that story is true, its point certainly is. Jesus summed up His teaching in the Sermon on the Mount…