يَحۡذَرُ ٱلۡمُنَٰفِقُونَ أَن تُنَزَّلَ عَلَيۡهِمۡ سُورَةٞ تُنَبِّئُهُم بِمَا فِي قُلُوبِهِمۡۚ قُلِ ٱسۡتَهۡزِءُوٓاْ إِنَّ ٱللَّهَ مُخۡرِجٞ مَّا تَحۡذَرُونَ
The hypocrites fear for a chapter being revealed regarding them, which may disclose what is hidden in their hearts; say, “Keep mocking; Allah will certainly disclose what you fear.”
Tafsir:
The Hypocrites fear Public Exposure of Their Secrets
Mujahid said, "The hypocrites would say something to each other then declare, `We wish that Allah does not expose this secret of ours," There is a similar Ayah to this one, that is, Allah's statement,
وَإِذَا جَآءُوكَ حَيَّوْكَ بِمَا لَمْ يُحَيِّكَ بِهِ اللَّهُ وَيَقُولُونَ فِى أَنفُسِهِمْ لَوْلاَ يُعَذِّبُنَا اللَّهُ بِمَا نَقُولُ حَسْبُهُمْ جَهَنَّمُ يَصْلَوْنَهَا فَبِئْسَ الْمَصِيرُ
(And when they come to you, they greet you with a greeting wherewith Allah greets you not, and say within themselves: "Why should Allah punish us not for what we say" Hell will be sufficient for them; they will burn therein. And worst indeed is that destination!) 58:8. Allah said in this Ayah,
قُلِ اسْتَهْزِءُواْ إِنَّ اللَّهَ مُخْرِجٌ مَّا تَحْذَرُونَ
(Say: "(Go ahead and) mock! But certainly Allah will bring to light all that you fear."), He will expose and explain your reality to His Messenger through revelation. Allah said in other Ayat,
أَمْ حَسِبَ الَّذِينَ فِى قُلُوبِهِمْ مَّرَضٌ أَن لَّن يُخْرِجَ اللَّهُ أَضْغَـنَهُمْ
(Or do those in whose hearts is a disease (of hypocrisy), think that Allah will not bring to light all their hidden ill-wills) 47:29, until,
وَلَتَعْرِفَنَّهُمْ فِى لَحْنِ الْقَوْلِ
(but surely, you will know them by the tone of their speech!)47:30. This is why, according to Qatadah, this Surah is called `Al-Fadihah' (the Exposing), because it exposed the hypocrites.