פרשת שופטים תשי"א - גדרי "לא תסור"

According to the law which they shall teach thee, and according to the judgment which they shall tell thee, thou shalt do; thou shalt not turn aside from the sentence which they shall declare unto thee, to the right hand, nor to the left.

ימין ושמאל [THOU SHALT NOT DEPART FROM THE WORD WHICH THEY SHALL TELL THEE] TO THE RIGHT NOR TO THE LEFT, even if he (the judge) tells you about what appears to you to be right that it is left, or about what appears to you to be left that it is right, you have to obey him; how much the more is this so if actually he tells you about what is evidently right that it is right and about what is left that it is left (cf. Sifrei Devarim 154:5).

Right or left: "Even if he tells you about the right that it is left or about the left that it is right" - [that is] the language of Rashi. And its matter is that even if you think in your heart that they are erring, and the thing is simple in your eyes - [just] like you know [the difference] between your right and your left - do like they command. And do not say, "How can I eat this completely forbidden fat" or "How can I kill this innocent man," but rather say, "So did the Master who commands command me to do with the commandments, that I should do His commandments, according to all that those that stand in front of Him - 'in the place that He shall choose' - instruct me; and He gave me the Torah upon the understanding of their minds, even if they err." And this is like the matter of Rabbi Yehoshua with Rabban Gamliel about Yom Kippur that fell out according to the calculation [of Rabbi Yehoshua] (Rosh Hashanah 25a). And the need for this commandment is very great, since the Torah is given to us in writing, and it is known that the opinions are not [all] the same concerning all of its implications. And [otherwise] the disagreements would grow and the Torah would become several Torahs. And the verse set forth that we should listen to the High Court that stands in front of God 'in the place that He shall choose,' about all that they tell us concerning the understanding of the Torah - whether they received its understanding, one witness from the mouth of another, and Moshe from the mouth of the Omnipotent; or they say thus according to the meaning of the Scripture. Or its intention is that in accordance with their opinion does He give them (other [variants of the text]: us) the Torah: even if it is in your eyes like the replacing of the right with the left; and all the more so, when they say about the right that is right - that you must think that the spirit of God is upon the servants of His Temple, 'and He will not leave His pious ones, they will always be protected' from erring and from stumbling. And the language of Sifrei on Shoftim 154 is "Even if they show to your eyes about the right that is the left and the left that it is the right, listen to them."