"You shall not be afraid before any man"—Deuteronomy 1:17.
A judge may not fear an evil and dangerous individual, ruling in his favor because he's concerned that he may exact revenge against him. As the Midrash says, "Perhaps you will say, 'I fear that individual for perhaps he will kill my son, set my barn afire, or destroy my crops'—therefore the Torah says, 'You shall not be afraid before any man!'"
