Дварим 16:19 Комментарий: Rashi, Ibn Ezra, Or HaChaim & Rabbeinu Bahya

לא תטה משפט means what it literally implies: THOU SHALT NOT PERVERT JUDGMENT.

You [singular] must not pervert justice Scripture addresses every individual judge.

לא תטה משפט, "Do not pervert justice, etc." This commandment is not only addressed to the judges but to all those who by failing to appoint the proper judiciary contribute to unfair judgments being handed down by unauthorised sources.

ולא תכיר פנים AND THOU SHALT NOT RESPECT PERSONS — not even if it be only during the pleadings of the parties. This is an admonition addressed to the judge that he should not be lenient to one and harsh to the other, e.g. letting one stand and the other sit; because as soon as he (the party treated harshly) observes that the judge shows more respect to his fellow his ability to plead is hampered (i.e. he loses self-confidence and cannot present his case with assurance) (cf. Shevuot 30a).