Sunan an-Nasa'i, Book 25, Hadith 81 (In-Book) ⓘ
It was narrated from Abu Hurairah that the Prophet said: "Allah, the Mighty and Sublime, likes it when there are two men, one of whom killed the other, then they both enter Paradise." And another time he said: "He laughs at two men, one of whom killed the other, then they both entered Paradise."
أَخْبَرَنَا مُحَمَّدُ بْنُ مَنْصُورٍ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " إِنَّ اللَّهَ عَزَّ وَجَلَّ يَعْجَبُ مِنْ رَجُلَيْنِ يَقْتُلُ أَحَدُهُمَا صَاحِبَهُ - وَقَالَ مَرَّةً أُخْرَى لَيَضْحَكُ مِنْ رَجُلَيْنِ يَقْتُلُ أَحَدُهُمَا صَاحِبَهُ - ثُمَّ يَدْخُلاَنِ الْجَنَّةَ " .
also referenced under: Hadith 3165 (Reference) & Volume 4, Book 25, Hadith 3167 (DarusSalam)