The Thunder - 13:9 He is the Knower of the hidden and the manifest, the Great, the Exalted.
It also refers to the hypocrites who harbor secret and evil thoughts and plans against Allah and His Messenger:
The Pleading Woman/58:8 "Have you not noticed those who were forbidden to hold secret meetings but still persist in what they were forbidden? They are lobbying for the purpose of sinning, enmity and disobeying the Messenger. When they come to you, they greet you in a way that Allah does not greet you. They say among themselves, "Why should Allah punish us for what we say!"Hell is enough for them. There they will burn; what an evil abode is that."

The Spoils of War/8:30 The disbelievers were plotting to neutralize you or to kill you or to drive you away. If they are plotting, Allah is plotting. Allah is the most skillful of plotters.

The Repentance/9:64 "The hypocrites fear the descent of a Surah which will inform them of what is in their hearts. Say: "Mock, Allah will reveal to you what you fear."

Muhammad/47:29 Do they not know that Allah will reveal their hatred to those in whose hearts is a disease?

The Women/4:80 He who follows the messenger follows Allah. Whoever turns away, let him turn away; We have not sent you as a watchman over them.
The Women/4:81 "They say: "All right, we obey". But when they leave you, some of them plot the opposite of what they said. Allah records what they plan and plot. Pay no attention to them; trust in Allah. Allah is sufficient as a supporter."

The Family Of Imran/3:119 "You are the ones who love them even though they do not love you! Moreover, you believe in all the Scriptures. When they meet you, they say: "We believe", but when they are alone, they bite their fingers out of anger against you. Say: "May you die in your anger."Surely Allah is Knower of the essence of the breasts."

The Victory/48:6 And punish the hypocritical men and hypocritical women and the idolatrous men and idolatrous women who harbor evil thoughts about Allah. Their evil deeds will backfire. Allah has wrath on them and cursed them and prepared Hell for them. What an evil place of return.
The Victory/48:12 Indeed, you thought that the apostle and the believers would not return to their families forever, and this thought was pleasant to your hearts. You were dreaming evil dreams, and in the end you became a lowly people.

The Table Spread/5:52 "You will see those in whose hearts is a disease, wandering among them, saying: "We fear that some calamity may befall us. It may happen that Allah will bring victory or a command from His side, and they will regret what they have been concealing in their hearts."

The Family Of Imran/3:154 "Then after that sorrow, He sent down upon you a safe sleep which calmed a group of you. Some of you were self-absorbed and self-centered, forming false ideas about Allah, as in the days of ignorance, and saying, "Do we have any authority in this matter?"Say, "All authority belongs to Allah."They were hiding in their hearts what they did not reveal to you. They say, "If we had any authority, we would not have been killed here."Say, "Even if you had been in your homes, those among you who were appointed to die would have crawled to the place where they would have fallen."Allah thus tries what is in your breasts and purifies what is in your hearts. Allah knows the most secret thoughts."
The Family Of Imran/3:167 "Thus are the hypocrites exposed. When it was said to them, "Come, fight in the way of Allah or contribute", they said, "If we knew about war, we would have joined you". At that moment they were closer to disbelief than to faith. They say with their mouths what is not in their hearts. But Allah knows very well what they conceal."

The Women/4:114 There is no good in most of their secret talks, except when they advocate charity or goodness or making amends between people. Whoever does these things seeking Allah´s pleasure, We shall give him a great reward.

The Table Spread/5:61 "When they came to you, they said: "We believe". But they entered you with their disbelief and left you with their disbelief. Allah knows better what they conceal."

Prophet Hud/11:5 They want to conceal from Him what is in their breasts. Know well that He knows what they conceal and what they reveal, even when they put on their clothes. He is the Knower of secret thoughts.

The Night Journey/17:47 "We know well how they hear when they listen to you, and how they say among themselves, "You are only following a bewitched man"."

The Cattle/6:25 "Some of them listen to you. But We put veils over their hearts to prevent them from understanding and weights over their ears. Even if they see every miracle, they do not believe in it. So when they come to you, they dispute with you, and the disbelievers say, "This is but a myth."

Muhammad/47:16 "There are some of them who listen to you. But when they leave you, they ask those to whom they have been given knowledge, "What did he say just now?"These are they whose hearts Allah has stamped, and they follow their desires."

The Women/4:60 Do you not see those who claim to believe in you and in what has been sent down to you and in what has been sent down before you, but they want to follow the laws of the unjust and despotic, while they were commanded to disbelieve in it, but Satan wants to lead them astray.

The Table Spread/5:41 "Do not let not the zeal of those who say with their mouths, "We believe"but do not believe with their hearts grieve you. There is a group of the Jews who listen to lies and listen to a people who have never met you. They twist the meaning of words. They say, "If this is given to you, take it, and if not, beware."If Allah wishes to mislead anyone, no one can help him against Allah. Those are they whose hearts Allah does not wish to purify. For them is humiliation in this world and a great torment in the Hereafter."

The Light/24:47 "They say: "We believe in Allah and the messenger and obey". But then, after that, a group of them turn away; they are not believers."
The Light/24:48 When they are called to Allah and His messenger to judge between them, a group of them dislike.
The Light/24:49 But if the decision is in their favor, they run to it willingly.
The Light/24:50 Is there a disease in their hearts? Do they doubt? Do they fear that Allah and His messenger will do them injustice? Indeed they are wrongdoers.

The Cow/2:14 "When they meet those who believe, they say, "We believe"; but when they are alone with their devils, they say, "We are with you. We are only mocking."

The Family Of Imran/3:72 "A group of the people of the Book said: "Believe in what has been sent down to the believers at the beginning of the day and disbelieve at the end. So that perhaps they may turn away from their religion."
The Family Of Imran/3:73 "Believe in none but he who follows your religion."Say to them, "The Guidance is Allah´s Guidance."And if they say to you, "Do not believe that another has been given the like of what has been given to you, lest they gain the right to dispute with you about your Lord,"say to them, "The bounty is in the hand of Allah, He gives it to whom He wills."Allah is Generous, All-Knowing."

The Hypocrites/63:1 "When the hypocrites come to you, they say, "We bear witness that you are the messenger of Allah. Allah knows that you are His messenger, and Allah testifies that the hypocrites lie."
The Hypocrites/63:2 They take their oaths as a shield and lead astray from the way of Allah. How evil is what they do.
The Hypocrites/63:3 Because they disbelieved after they believed, so their hearts were sealed; they do not understand.
The Hypocrites/63:4 When you see them, you like their appearance. If they speak, you listen to their words. They are like stumps that stand upright. They think every noise is against them; they are the real enemies; beware of them. May Allah curse them; how they turn away!
The Hypocrites/63:5 "When it is said to them, "Come, so that the messenger of Allah may ask forgiveness for you,"they turn their heads away, and you see them straying arrogantly."

The Cow/2:8 "There are such among the people who say: "We believe in Allah and the Last Day"when in fact they do not believe."
The Cow/2:9 They seek to deceive Allah and the believers. However, they deceive themselves. They do not even realize it.
The Cow/2:75 Do you hope that they will believe in you, whereas some of them, after hearing the word of Allah, would deliberately change it.
The Cow/2:76 "When they meet the believers, they say: "We believe"; but when they are alone with them, they say: "Do you tell them what Allah has revealed to you so that they may use it as evidence against you in the sight of your Lord?"
The Cow/2:77 Do they not know that Allah knows all that they conceal and all that they reveal?

The Table Spread/5:59 "Say: "People of the Book! Do you hate us because we believe in Allah and what has been sent down to us and what was sent down before?"
The Table Spread/5:60 "Say: "Shall I inform you of something worse than this in the sight of Allah? Whom Allah has cursed and wrathfully turned into apes, pigs and idolaters, those are the worst in the land and the most astray from the right path."
The Table Spread/5:61 "When they came to you, they said: "We believe". But they entered you with their disbelief and left you with their disbelief. Allah knows better what they conceal."
The Table Spread/5:62 You see most of them running about in sin and enmity and forbidden food. How evil is what they do!

The Women/4:107 Defend those who betray their own selves; Allah does not love those who betray and sin.
The Women/4:108 They hide from the people, but they cannot hide from Allah. He is with them when they conceive thoughts that He dislikes. Allah encompasses all that they do.