closed doors in the depths of the night. On the Day of Judgement, however, no action will be hidden. The smallest of the small and the largest of the large will all be visible.

Allah declares:

فَمَنۡ یَّعۡمَلۡ مِثۡقَالَ ذَرَّۃٍ خَیۡرًا یَّرَہٗ ؕ(۷)وَ مَنۡ یَّعۡمَلۡ مِثۡقَالَ ذَرَّۃٍ  شَرًّا یَّرَہٗ (۸)

 So, whosoever does a good deed equal to the weight of an atom, (he) shall see it. And whoever does an evil deed equal to the weight of an atom, (he) shall see it.^[1]

No sin can be hidden

Luqmān the Wise رَحْمَةُ الـلّٰـهِ عَلَيْه, a pious man of Allah known for his wisdom and sagacity, once gave advice to his son. This is even mentioned in the Quran:

یٰبُنَیَّ  اِنَّہَاۤ  اِنۡ تَکُ مِثۡقَالَ حَبَّۃٍ  مِّنۡ خَرۡدَلٍ فَتَکُنۡ فِیۡ صَخۡرَۃٍ  اَوۡ فِی السَّمٰوٰتِ اَوۡ فِی الۡاَرۡضِ یَاۡتِ بِہَا اللّٰہُ ؕ اِنَّ اللّٰہَ  لَطِیۡفٌ خَبِیۡرٌ (۱۶)

'O my son! If the evil deed is equal to the weight of a mustard seed, it is then in a rock, or in the heavens, or wherever in the earth, Allah will bring it forth; indeed, Allah is the Knower of every subtlety, the All-Aware.'^[2]

So evil, no matter how minor and hidden as it might seem, will be brought forth on the Day of Judgement. Indeed, Allah knows absolutely everything and He is All-Aware.