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Surah 9. Al-Tawba
Ayah 75 - 78
75 وَمِنْهُم مَّنْ عَـٰهَدَ ٱللَّهَ لَئِنْ ءَاتَىٰنَا مِن فَضْلِهِۦ لَنَصَّدَّقَنَّ وَلَنَكُونَنَّ مِنَ ٱلصَّـٰلِحِينَ
76 فَلَمَّآ ءَاتَىٰهُم مِّن فَضْلِهِۦ بَخِلُوا۟ بِهِۦ وَتَوَلَّوا۟ وَّهُم مُّعْرِضُونَ
77 فَأَعْقَبَهُمْ نِفَاقًا فِى قُلُوبِهِمْ إِلَىٰ يَوْمِ يَلْقَوْنَهُۥ بِمَآ أَخْلَفُوا۟ ٱللَّهَ مَا وَعَدُوهُ وَبِمَا كَانُوا۟ يَكْذِبُونَ
78 أَلَمْ يَعْلَمُوٓا۟ أَنَّ ٱللَّهَ يَعْلَمُ سِرَّهُمْ وَنَجْوَىٰهُمْ وَأَنَّ ٱللَّهَ عَلَّـٰمُ ٱلْغُيُوبِ
75. And of them are some who made a covenant with Allah (saying): "If He bestowed on us of His bounty, we will verily, give Sadaqah and will be certainly among the righteous.'' 76. Then when He gave them of His bounty, they became stingy, and turned away, averse. 77. So He punished them by putting hypocrisy into their hearts till the Day whereon they shall meet Him, because they broke that (covenant) with Allah which they had promised to Him and because they used to tell lies. 78. Know they not that Allah knows their secret ideas, and their Najwa (secret counsels), and that Allah is the All-Knower of things unseen.
Allah says, some hypocrites give Allah their strongest oaths that if He enriches them from His bounty, they will give away alms and be among the righteous. However, they did not fulfill their vows or say the truth with their words. The consequence of this action is that hypocrisy was placed in their hearts until the Day they meet Allah the Exalted, on the Day of Resurrection. We seek refuge with Allah from such an end. Allah said,
(...because they broke that (covenant) with Allah which they had promised to Him) He placed hypocrisy in their hearts because they broke their promise and lied. In the Two Sahihs, it is recorded that the Messenger of Allah said,
(There are three signs for a hypocrite: if he speaks, he lies; if he promises, he breaks the promise; and if he is entrusted, he betrays the trust.) Allah said,
(Know they not that Allah knows their secret ideas, and their Najwa,) Allah states that He knows the secret and what is more hidden than the secret. He has full knowledge of what is in their hearts, even when they pretend that they will give away alms, if they acquire wealth, and will be grateful to Allah for it. Truly, Allah knows them better than they know themselves, for He is the All-Knower of all unseen and apparent things, every secret, every session of counsel, and all that is seen and hidden.