Sunan an Nasai
3165
Sahih+2

It was narrated from Abu Hurairah that the Prophet (ﷺ) 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

SahihAbu Ghuddah
SahihAl-Albani