Matar a cobra e mostrar o pau

Literally: To kill the snake and show the stick

Example: “Diz que correu a maratona? Então mata a cobra e mostra o pau: cadê a medalha?” — He says he ran the marathon? Then let him prove it: where's the medal?

Origin: Rooted in genuinely rural Brazilian life, particularly the country's northeast, from a time when snakebite was a real and immediate danger for anyone working outdoors, and killing a venomous snake with whatever stick or branch happened to be at hand was an ordinary act of self-defense. Bringing the stick back along with proof of the kill — showing exactly what had happened rather than simply reporting it — served as concrete, undeniable evidence in a rural culture where a spoken account, however dramatic, could easily be doubted without something to back it up. Over time the phrase broadened well past snakes and sticks into a general expression for backing up any claim with hard, checkable proof rather than leaving it as an unverified story.