﴿ يَحْذَرُ ٱلْمُنَٰفِقُونَ أَن تُنَزَّلَ عَلَيْهِمْ سُورَةٌۭ تُنَبِّئُهُم بِمَا فِى قُلُوبِهِمْ ۚ قُلِ ٱسْتَهْزِءُوٓا۟ إِنَّ ٱللَّهَ مُخْرِجٌۭ مَّا تَحْذَرُونَ ﴾

“[Some of] the hypocrites dread lest a [new] surah be revealed [in evidence] against them, making them understand what is [really] in their hearts. Say: "Go on mocking! Behold, God will bring to light the very thing that you are dreading!"”

The hypocrites are cautious they fear lest a sūra should be revealed to them that is to the believers informing them of what is in their the hypocrites’ hearts of hypocrisy and yet despite this they persist in mockery. Say ‘Keep mocking! this is an imperative of threat God will bring out He will make manifest that hypocrisy of yours of which you are fearful’ lest it be brought out.