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What is done at night comes to light by day.
Literal
Night do-[past-た] things [topic-は] day appear.
A proverb-like statement — 'nighttime deeds show in the day.' Short, parallel, aphoristic. 夜 and 昼 are paired without particles (bare noun-as-adverb use for time), 行った is the past form of 行う ('do, perform, carry out'), more formal than する. 現れる ('appear, emerge, come to light') completes the hidden→visible arc.