فَأَعۡقَبَهُمۡ نِفَاقٗا فِي قُلُوبِهِمۡ إِلَىٰ يَوۡمِ يَلۡقَوۡنَهُۥ بِمَآ أَخۡلَفُواْ ٱللَّهَ مَا وَعَدُوهُ وَبِمَا كَانُواْ يَكۡذِبُونَ
So following this, Allah put hypocrisy in their hearts until the day when they will meet Him – the result of their breaching the promise made to Allah, and because they lied.
Tafsir:
Hypocrites seek Wealth but are Stingy with Alms
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,
بِمَآ أَخْلَفُواْ اللَّهَ مَا وَعَدُوهُ
(...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 ﷺ said,
«آيَةُ الْمُنَافِقِ ثَلَاثٌ: إِذَا حَدَّثَ كَذَبَ، وَإِذَا وَعَدَ أَخْلَفَ، وَإِذَا ائْتُمِنَ خَان»
(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,
أَلَمْ يَعْلَمُواْ أَنَّ اللَّهَ يَعْلَمُ سِرَّهُمْ وَنَجْوَاهُمْ
(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.