Therefore...
Therefore, the Qur'an introduces the unreasonable murder of a person like slaying all the human-kind in the world. So, if a person kills another human being without that the slain be a murderer or a mischief monger on the earth, it seems he has killed all human-kind.
Surah An-Nisa', Verse 94 يَا أَيُّهَا الَّذِينَ آمَنُواْ إِذَا ضَرَبْتُمْ فِي سَبِيلِ اللّهِ فَتَبَيَّنُواْ وَلاَ تَقُولُواْ لِمَنْ أَلْقَى إِلَيْكُمُ السَّلاَمَ لَسْتَ مُؤْمِنًا تَبْتَغُونَ عَرَضَ الْحَيَاةِ الدُّنْيَا فَعِندَ اللّهِ مَغَانِمُ كَثِيرَةٌ كَذَلِكَ كُنتُم مِّن قَبْلُ فَمَنَّ اللّهُ عَلَيْكُمْ فَتَبَ
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