Sunan an Nasai
4126
Sahih+2

It was narrated that Ibn 'Umar said:"The Messenger of Allah [SAW] said: 'Do not revert to disbelievers after I am gone, striking the necks of one another (killing one another). No man is to be punished for the sins of his father, or for the sins of his brother

SahihAbu Ghuddah
SahihAl-Albani