Abu Saeed Khudri reported,

The Prophet ﷺ said that a man had killed ninety-nine people, and he began to ask whether there was any path to repentance for him. He came to a monk and asked him, and the monk said, "There is no repentance for you." So he killed the monk as well.Then he continued asking, and he set out from his village toward another village in which there were righteous people. While he was on the way, death overtook him. He stretched out his chest toward that village and then died. The angels of mercy and the angels of punishment disputed over him. He was found to be closer to the righteous village by a hand's breadth, so he was counted among its people.

Muslim 7009

Sahih

حدثني عبيد الله بن معاذ العنبري حدثنا أبي حدثنا شعبة عن قتادة أنه سمع أبا الصديق الناجي

عن أبي سعيد الخدري

عن النبي ﷺ أن رجلا قتل تسعة وتسعين نفسا فجعل يسأل هل له من توبة فأتى راهبا فسأله فقال ليست لك توبة فقتل الراهب ثم جعل يسأل ثم خرج من قرية إلى قرية فيها قوم صالحون فلما كان في بعض الطريق أدركه الموت فنأى بصدره ثم مات فاختصمت فيه ملائكة الرحمة وملائكة العذاب فكان إلى القرية الصالحة أقرب منها بشبر فجعل من أهلها

مسلم 7009صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Muslim
Book
Tawba
Chapter
Acceptance of the repentance of a killer even if his killing was frequent
Numbering
Darussalam 7009
Muslim 7009