Allah (swt) wants to assure humans, particularly the believers in His existence, that He knows the secret and what’s beyond it. Thus, the Almighty knows your deeds and what’s there within yourself wherever and in whatever manner you are. Allah (swt) owns the skies and Earth:

 {لِلَّهِ مُلْكُ السَّمَاوَاتِ وَالْأَرْضِ وَمَا فِيهِنَّ ۚ وَهُوَ عَلَىٰ كُلِّ شَيْءٍ قَدِيرٌ}

(To Allah belongs the dominion of the heavens and the earth and whatever is within them. And He is over all things competent.) (Al-Maaida: 120)

So, He is the One who’s running the affairs of all creatures as He states in (verse 2) at the beginning of this Sura:

{ اللَّهُ لَا إِلَٰهَ إِلَّا هُوَ الْحَيُّ الْقَيُّومُ}

(Allah – there is no deity except Him, the Ever-Living, the Sustainer of existence.) (Aal-Imran: 2)

And nothing in heavens or earth is hidden from the Sustainer of all existence. There can’t be any ethics or values without the control of the religion which, in turn, stems out of man’s awareness that nothing can be hidden from Allah (swt). Such control, and such awareness that Allah is always there knowing and hearing, if any, is the guarantee that no one will dare do commit deadly sins such as telling lies, slander, backbiting, theft, adultery, bribery, drinking wine, … etc.