To watch one's step / to be on guard
Quando vi a confusão começando, botei as barbas de molho.
When I saw the trouble starting, I knew to watch my step.
Traced to a Spanish proverb: Cuando las barbas de tu vecino veas pelar, pon las tuyas a remojar — 'when you see your neighbour's beard being shaved, put yours to soak.' In medieval and early-modern culture a man's beard symbolized honour; having it shaved was a public humiliation.
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