Quran 47:20

وَيَقُولُ ٱلَّذِينَ ءَامَنُواْ لَوۡلَا نُزِّلَتۡ سُورَةٌ۬‌ۖ فَإِذَآ أُنزِلَتۡ سُورَةٌ۬ مُّحۡكَمَةٌ۬ وَذُكِرَ فِيہَا ٱلۡقِتَالُ‌ۙ رَأَيۡتَ ٱلَّذِينَ فِى قُلُوبِہِم مَّرَضٌ۬ يَنظُرُونَ إِلَيۡكَ نَظَرَ ٱلۡمَغۡشِىِّ عَلَيۡهِ مِنَ ٱلۡمَوۡتِ‌ۖ فَأَوۡلَىٰ لَهُمۡ ٢٠

Those who believed said: "When will a new Sura be revealed?" But when a straightforward Sura was revealed, wherein fighting was mentioned, you would see those who harbored doubts in their hearts looking at you, as if death had already come to them. They were thus exposed.