Sunan an-Nasa'i, Book 37, Hadith 23 (In-Book) ⓘ
It was narrated that 'Abdullah bin 'Amr said: "Killing a believer is more grievous before Allah than the extinction of the whole world."
أَخْبَرَنَا مُحَمَّدُ بْنُ بَشَّارٍ، قَالَ حَدَّثَنَا مُحَمَّدٌ، عَنْ شُعْبَةَ، عَنْ يَعْلَى، عَنْ أَبِيهِ، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو، قَالَ قَتْلُ الْمُؤْمِنِ أَعْظَمُ عِنْدَ اللَّهِ مِنْ زَوَالِ الدُّنْيَا .
also referenced under: Hadith 3988 (Reference) & Volume 5, Book 37, Hadith 3993 (DarusSalam)