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 ‏"‏ ‏.‏

It was narrated from Abu Hurairah that the Prophet (PBUH) 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." Translation Not Available

Book Ref: Sunan An Nisai Book 25 Hadith 3165
Web Ref:  Sunan An Nisai Vol 1 Book 25 Hadith 3167