The Book of Fighting [The Prohibition of Bloodshed]
37/2. Chapter:
The Gravity of the Sin of Shedding Blood
Sunan an-Nasai
أَخْبَرَنَا سَرِيعُ بْنُ عَبْدِ اللَّهِ الْوَاسِطِيُّ الْخَصِيُّ، قَالَ حَدَّثَنَا إِسْحَاقُ بْنُ يُوسُفَ الأَزْرَقُ، عَنْ شَرِيكٍ، عَنْ عَاصِمٍ، عَنْ أَبِي وَائِلٍ، عَنْ عَبْدِ اللَّهِ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أَوَّلُ مَا يُحَاسَبُ بِهِ الْعَبْدُ الصَّلاَةُ وَأَوَّلُ مَا يُقْضَى بَيْنَ النَّاسِ فِي الدِّمَاءِ " .
It was narrated that 'Abdullah said: "The Messenger of Allah [SAW] said: 'The first thing concerning which a person will be brought to account will be the Salah, and the first thing concerning which scores will be settled among the people, will be bloodshed."
Reference : Sunan an-Nasa'i 3991In-book reference : Book 37, Hadith 26English translation : Vol. 5, Book 37, Hadith 3996