(Muhammed) 47 : 20
وَيَقُولُ الَّذِينَ آمَنُوا لَوْلَا نُزِّلَتْ سُورَةٌ ۖ فَإِذَا أُنْزِلَتْ سُورَةٌ مُحْكَمَةٌ وَذُكِرَ فِيهَا الْقِتَالُ ۙ رَأَيْتَ الَّذِينَ فِي قُلُوبِهِمْ مَرَضٌ يَنْظُرُونَ إِلَيْكَ نَظَرَ الْمَغْشِيِّ عَلَيْهِ مِنَ الْمَوْتِ ۖ فَأَوْلَىٰ لَهُمْ

And those who believed say: Why is not a Surah sent down? Then if a Wise Surah has been sent down, and in It mentions about the war, you can see those who are having diseases in their hearts staring into you with a look of fearing of death, then it is most suitable for them.

Battles and trials are happened by Lord Allah in order to distinguish the Hypocrites and the believers. If the believers are living here with the aim of life understood from Lord’s Book Adhikr and are entrusting all their affairs upon Allah who controls everything, the hypocrites are living here by forgetting Allah and the aim of life preferring bodily and worldly life. So if they are called to the battle, they are considering it as if they are called to the death, and so they are showing horribleness. Such are those who lost this worldly life and the Hereafter. See explanation 4: 77-79; 9: 64-65; and 33: 12-13, 19.