The Gemara mentions a popular saying of their time, “לֵךְ לְךָ אָמְרִינַן נְזִירָא, סְחוֹר סְחוֹר, לְכַרְמָא לָא תִּקְרַב״. Go around, go around, and do not approach the vineyard, they say to the nazirite.”

This adage is used countless times in halakhic literature to support the importance of creating safety nets around prohibited item. Just as the Nazir is advised to stay away from the vineyard, even if he does not drink the wine, so too a person should take extra caution and keep a distance from what is forbidden.

The problem with this adage is that there is no such literal halakha or recommendation. There is nothing wrong with a Nazir going into a vineyard. Interestingly the Rambam (Mishne Torah, Nazir 5:10) does cite a rabbinic prohibition to enter a place where people are gathered to drink wine. There is no explicit mention of this in the Gemara, but Kesef Mishne (Op. Cit.) indicates this adage as the source. Regardless, there is no prohibition whatsoever against a Nazir from entering a vineyard. Clearly then the statement is metaphorical, but what is the source of this idea? Why not just cite the concept of from Avos (1:1) עשו סייג לתורה, make a fence around the Torah?

Additionally, the phrase itself is difficult to parse. Let’s analyze it word by word:

לך לך go, go

אמרינן נזירא does this mean , “we say to the Nazir?” If so, it should be written with a Lamed, Le-Nezira לנזירא?

In fact, there are a number of Rishonim that use the phrase  “Le-Nezira “, to the Nazir 

לנזירא

However, the standard text in the Gemaras and most of the commentaries is נזירא. So, we might consider the phrase as, “Go, go, oh Nazir”, we say. Instead of, “we say to the Nazir…

In any case, the meaning would seem to be the same. Once again, where does this phrase originate from?

I believe this is not merely a folk saying but actually derived from the verses regarding a Nazir. The verse (Bamidbar 6:3) states four different prohibitions:

מִיַּ֤יִן וְשֵׁכָר֙ יַזִּ֔יר חֹ֥מֶץ יַ֛יִן וְחֹ֥מֶץ שֵׁכָ֖ר לֹ֣א יִשְׁתֶּ֑ה וְכָל־מִשְׁרַ֤ת עֲנָבִים֙ לֹ֣א יִשְׁתֶּ֔ה וַעֲנָבִ֛ים לַחִ֥ים וִיבֵשִׁ֖ים לֹ֥א יאכֵֽל׃

he shall abstain from (1) wine and any other intoxicant; (2) he shall not drink vinegar of wine or of any other intoxicant, (3) neither shall he drink anything in which grapes have been steeped, (4) nor eat grapes fresh or dried.

The prohibitions go in order of severity. First actual wine is forbidden, then vinegar wine, then something soaked in grapes or wine, then the grapes themselves.

The final category is most likely not even intoxicating and yet the Torah is still forbidding the Nazir from eating grapes. Presumably, the reason is because it is an extra safeguard to keep the Nazir away from temptation. Therefore, we see a situation where the Torah is building in a safeguard, implying that such safeguards are virtuous. Given this, it is really as if the Torah is metaphorically instructing the Nazir to even stay away from the vineyard. And so, the concept of creating a fence around the Torah while rabbinic, has a source within the Biblical laws as well.