Mishnah — Seder Nezikin, Tractate SanhedrinChapter 3…
“ It is an explanation of what disqualifies a person from serving as a witness or judge, based on their interpersonal relationship to the litigants, rather than by their profession or blood relation. Anyone who 'loves' or 'hates' one of the litigants can't serve, as they would undoubtedly be biased. Love is explained as such that a groomsman would have, and hatred is explained as that which would drive a wedge of silence between two people due to anger. ”
