Proverbs 17:27-18:1

New International Version

²⁷ The one who has knowledge uses words with restraint,^(A)
    and whoever has understanding is even-tempered.^(B)

²⁸ Even fools are thought wise if they keep silent,
    and discerning if they hold their tongues.^(C)

18 An unfriendly person pursues selfish ends
    and against all sound judgment starts quarrels.