עַל־פִּ֨י הַתּוֹרָ֜ה אֲשֶׁ֣ר יוֹר֗וּךָ וְעַל־הַמִּשְׁפָּ֛ט אֲשֶׁר־יֹאמְר֥וּ לְךָ֖ תַּעֲשֶׂ֑ה לֹ֣א תָס֗וּר מִן־הַדָּבָ֛ר אֲשֶׁר־יַגִּ֥ידֽוּ לְךָ֖ יָמִ֥ין וּשְׂמֹֽאל׃
You shall act in accordance with the instructions given you and the ruling handed down to you; you must not deviate from the verdict that they announce to you either to the right or to the left.
Torah Temimah points to Sanhedrin / Sifrei.
על פי התורה. אשר יורוך — מלמד שמורים לך את התורה.
English: According to the Torah that they instruct you — this teaches that they instruct you in the Torah.
The court’s role is to teach and apply the Torah, not to invent new law.
Derash on the verse (Bavli / Sifrei) — not a formal named middah of the 13.
The high court’s verdict is an instruction in the existing Torah.