▼ The term רִיב (riv) can mean “quarrel” or “legal accusation” (BDB 936 s.v.). Both ideas would work but the more technical legal accusation fits the context better. This is a warning to not bring legal accusations against anyone without a legitimate reason.

▼ Heb “a man.”

▼ Heb “gratuitously”; NIV, TEV “for no (+ good NCV) reason.” The adverb חִנָּם (khinam) means “without cause, undeservedly,” especially of groundless hostility (HALOT 334 s.v. 3; BDB 336 s.v. c).