you scratch my back and I'll scratch yours
Somos amigos, uma mão lava a outra!
We're friends, you scratch my back and I'll scratch yours!
The saying uma mão lava a outra ("one hand washes the other") is a classical proverb. It appears in Latin as manus manum lavat in Seneca's satire the Apocolocyntosis (1st century AD), and the idea is older still, going back to the Greek comic poet Epicharmus.
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