Abu Hurairah reported,
The Prophet ﷺ said, "Allah 
marvels at two men, one of whom kills the other," and another time he said, "Allah laughs at two men, one of whom kills the other, then both enter Paradise."
Nasai 3167
Sahihأخبرنا محمد بن منصور قال حدثنا سفيان عن أبي الزناد عن الأعرج
عن أبي هريرة
عن النبي ﷺ قال إن الله عز وجل يعجب من رجلين يقتل أحدهما صاحبه وقال مرة أخرى ليضحك من رجلين يقتل أحدهما صاحبه ثم يدخلان الجنة
No references are available.
Reported by Muslim, Emirate, chapter on the explanation that two men, one of whom kills the other, both enter Paradise, hadith no. 1890, from the hadith of Sufyan bin Uyayna, and Bukhari, Jihad and Expeditions, chapter on the disbeliever who kills a Muslim then embraces Islam and is upright thereafter and is killed, hadith no. 2826, from the hadith of Abu Zinad, through the same chain, and it is in al-Kubra, hadith no. 4373.