Abu Umama bin Sahl reported,

We were with Uthman while he was besieged in his house when he said, "Why are you trying to kill me? I heard the Messenger of Allah ﷺ say, 'The blood of a Muslim is not lawful to shed except for one of three reasons, a man who disbelieves after his Islam, or commits adultery after marriage, or kills a person and is killed in retaliation.'"

Ahmad 509

Sahih

حدثنا سليمان بن حرب حدثنا حماد بن زيد عن يحيى بن سعيد

عن أبي أمامة بن سهل بن حنيف قال

كنا مع عثمان وهو محصور في الدار قال ولم تقتلونني سمعت رسول الله ﷺ يقول لا يحل دم امرئ مسلم إلا بإحدى ثلاث رجل كفر بعد إسلامه أو زنى بعد إحصانه أو قتل نفسا فيقتل بها

أحمد 509صحيح
Contents
Reference
Commentary
Ayat
Collection
Musnad Ahmad
Book
Uthman bin Affan
Numbering
Darussalam 509
Ahmad 509