proverb/le p(ə).ti ʁɥi.so fɔ̃ le ɡʁɑ̃d ʁi.vjɛʁ/
many a mickle makes a muckle; little strokes fell great oaks; mighty oaks from little acorns grow; take care of the pennies and the pounds will take care of themselves; every little helps
Literally, “small streams make big rivers”.