Allah declares that His knowledge is encompassing all of His creation, those who declare their speech or hide it, He hears it and nothing of it ever escapes His observation. Allah said in other Ayat,

[وَإِن تَجْهَرْ بِالْقَوْلِ فَإِنَّهُ يَعْلَمُ السِّرَّ وَأَخْفَى ]

(And if you speak aloud, then verily, He knows the secret and that which is yet more hidden.)[20:7], and,

[وَيَعْلَمُ مَا تُخْفُونَ وَمَا تُعْلِنُونَ]

(And (Allah) knows what you conceal and what you reveal.) `A'ishah said, "All praise is due to Allah Whose hearing has encompassed all voices! By Allah, she who came to complain about her husband to the Messenger of Allah was speaking while I was in another part of the room, yet I did not hear some of what she said. Allah sent down,

[قَدْ سَمِعَ اللَّهُ قَوْلَ الَّتِى تُجَادِلُكَ فِى زَوْجِهَا وَتَشْتَكِى إِلَى اللَّهِ وَاللَّهُ يَسْمَعُ تَحَاوُرَكُمآ إِنَّ اللَّهَ سَمِيعٌ بَصِيرٌ ]

(Indeed Allah has heard the statement of her that disputes with you concerning her husband and complains to Allah. And Allah hears the argument between you both. Verily, Allah is All-Hearer, All-Seer.)[58:1] Allah said next,

[وَمَنْ هُوَ مُسْتَخْفٍ بِالَّيْلِ]

(whether he be hid by night), in his house in the darkness of the night,

[وَسَارِبٌ بِالنَّهَارِ]

(or goes forth freely by day.) moves about during the daylight; both are encompassed by Allah's knowledge. Allah said in other Ayat,

[أَلا حِينَ يَسْتَغْشُونَ ثِيَابَهُمْ]

(Surely, even when they cover themselves with their garments.) [11:5], and,

[وَمَا تَكُونُ فِى شَأْنٍ وَمَا تَتْلُواْ مِنْهُ مِن قُرْءَانٍ وَلاَ تَعْمَلُونَ مِنْ عَمَلٍ إِلاَّ كُنَّا عَلَيْكُمْ شُهُودًا إِذْ تُفِيضُونَ فِيهِ وَمَا يَعْزُبُ عَن رَّبِّكَ مِن مِّثْقَالِ ذَرَّةٍ فِي الاٌّرْضِ وَلاَ فِى السَّمَآءِ وَلاَ أَصْغَرَ مِن ذَلِكَ وَلا أَكْبَرَ إِلاَّ فِى كِتَابٍ مُّبِينٍ ]

(Neither you do any deed nor recite any portion of the Qur'an nor you do any deed, but We are witness thereof when you are doing it. And nothing is hidden from your Lord (so much as) the a speck of dust on the earth or in the heaven. Not what is less than that or what is greater than that but is (written) in a Clear Record.)[10:61]