أَبى الله أنْ يَجْعَلَ لِقَاتِلِ المُؤمِنِ تَوْبَةً
It is reported from Anas bin Malik, that the Prophet (peace and blessings of Allaah be upon him) said:
“Allah refuses to accept the repentance of the murderer of a believer.”
This hadeeth was transmitted by al-Tabarani in al-Mu’jam al-Kabir and ad-Diyay al-Maqdisi to al-Muhtara (2164) from the words of Anas ibn Malik, may Allah be pleased with him.
Also in al-Silsila as-sahiha (689).