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 ﷺ 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

The Guardian Angels

Allah said next,

لَهُ مُعَقِّبَـتٌ مِّن بَيْنِ يَدَيْهِ وَمِنْ خَلْفِهِ يَحْفَظُونَهُ مِنْ أَمْرِ اللَّهِ

(For him (each person), there are angels in succession, before and behind him. They guard him by the command of Allah.) Allah states that there are angels who take turns guarding each servant, some by night and some by day. These angels protect each person from harm and accidents. There are also angels who take turns recording the good and evil deeds, some angels do this by day and some by night. There are two angels, one to the right and one to the left of each person, recording the deeds. The angel to the right records the good deeds, while the angel to the left records the evil deeds. There are also two angels that guard and protect each person, one from the back and one from in front. Therefore, there are four angels that surround each person by day and they are replaced by four others at night, two scribes and two guards. An authentic Hadith states,

«يَتَعَاقَبُونَ فِيكُمْ مَلَائِكَةٌ بِاللَّيْلِ وَمَلَائِكَةٌ بالنَّهَارِ، وَيَجْتَمِعُونَ فِي صَلَاةِ الصُّبْحِ وَصَلَاةِ الْعَصْرِ، فَيَصْعَدُ إِلَيْهِ الَّذِينَ بَاتُوا فِيكُمْ فَيَسْأَلُهُمْ وَهُوَ أَعْلَمُ بِكُمْ: كَيْفَ تَرَكْتُمْ عِبَادِي؟ فَيَقُولُونَ: أَتَيْنَاهُمْ وَهُمْ يُصَلُّونَ، وَتَرَكْنَاهُمْ وَهُمْ يُصَلُّون»

(Angels take turns around you, some at night and some by day, and all of them assemble together at the time of the Fajr and `Asr prayers. Then those who have stayed with you throughout the night, ascend to Allah Who asks them, and He knows the answer better than they about you, "How have you left My servants" They reply, "As we have found them praying, we have left them praying.") Imam Ahmad recorded that `Abdullah said that the Messenger of Allah ﷺ said,

«مَا مِنْكُمْ مِنْ أَحَدٍ إِلَّا وَقَدْ وُكِّلَ بِهِ قَرِينُهُ مِنَ الْجِنِّ وَقَرِينُهُ مِنَ الْمَلَائِكَة»

(Verily, every one among you has his companion from the Jinn and his companion from the angels.") They said, "And you too, O Allah's Messenger" He said,

«وَإِيَّايَ، وَلَكِنَّ اللهَ أَعَانَنِي عَلَيْهِ، فَلَا يَأْمُرُنِي إِلَّا بِخَيْر»

(And I too, except that Allah has helped me against him, so he only orders me to do good.) Muslim collected this Hadith. Ibn Abi Hatim narrated that Ibrahim said, "Allah revealed to a Prophet from among the Children of Israel, `Say to your nation: every people of a village or a house who used to obey Allah but changed their behavior to disobeying Him, then He will take away from them what they like and exchange it for what they dislike." Ibrahim next said that this statement has proof in Allah's Book,

إِنَّ اللَّهَ لاَ يُغَيِّرُ مَا بِقَوْمٍ حَتَّى يُغَيِّرُواْ مَا بِأَنفُسِهِمْ

(Verily, Allah will not change the (good) condition of a people as long as they do not change their state (of goodness) themselves.)