Mishkat al-Masabih 16 Retaliation كتاب القصاص 19

وَعَنْ أَبِي الدَّرْدَاءِ عَنْ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «لَا يَزَالُ الْمُؤْمِنُ مُعْنِقًا صَالِحًا مَا لَمْ يُصِبْ دَمًا حَرَامًا فَإِذَا أَصَابَ دَمًا حَرَامًا بَلَّحَ» . رَوَاهُ أَبُو دَاوُد

Abu ad-Darda’ reported God’s Messenger as saying, “A believer will continue to go on quickly and well* so long as he does not kill anyone unlawfully, but when he does so he will grow weary.” Abu Dawud transmitted it. *i.e. quick to obey God’s commands and observing well what is due to God and man.