A second century rabbinic text describes the objectives of a rabbi or a Torah teacher in the following way: The sages said “three things: be deliberate in judgment, raise up many disciples, and make a fence around the Torah” (Mishnah, Avot 1:1). The first two of these injunctions make sense, but what is a “fence around the Torah”?
Just like a physical fence, a fence around the Torah is a protective enclosure around a commandment; in other words, an extra layer of rules. First one has to scale the protective fence, and only then be in a position to transgress the actual holy commandment. This way, it will be more difficult for people to transgress the Torah. And as rabbis of his day, Jesus built fences around commandments too!
“You have heard that it was said, ‘You shall not commit adultery’; but I say to you that everyone who looks at a woman with lust for her has already committed adultery with her in his heart” (Matt 5:27-28).
First, Yeshua quoted the original commandment (Exodus 20:14) and added, “But I say to you…” and then comes Jesus’ fence: “avoid lustful gazing.” According to Jesus’ wisdom, adultery and unfaithfulness come from looking at someone or something that is not yours, and suddenly the desire is born. Jesus says that this is already a sin. But merely looking at people is not prohibited in Torah. The fence is to avoid inappropriate gazing that leads to inappropriate desires, so that one will not commit the actual sin of adultery. This is an example of Jesus building a fence around a biblical commandment, as was the practice of many other rabbis of his day.