"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."
Sunan an-Nasa'i Book 25, Hadith 81
← Previous Hadith "The martyrs and those who dies in their beds referred a dispute to our Lord concerning those who dies of the plague. The martyrs said: 'Our brothers were killed as we were killed.' And those who dies in their beds said: 'Our brothers dies on their beds as we died.' Our Lord said: 'Look at their wounds; if their wounds; if their wounds are like the wounds of those who were killed then they are of them and belong with them.' And their wounds were like their (the martyrs') wounds."

Sunan an-Nasa'i Book 25, Hadith 80 Next Hadith → "Allah laughs at two men, one of whom killed the other but they both entered Paradise. The first one fought in the cause of Allah and was killed, then Allah accepted the repentance of the one who killed him, and he fought and was martyred."

Sunan an-Nasa'i Book 25, Hadith 82