Miqdad bin Amr reported,

He said to the Messenger of Allah ﷺ, "Tell me, if I meet a man from the disbelievers and we fight, and he strikes one of my hands with the sword and cuts it off, then takes refuge from me behind a tree and says, 'I have submitted to Allah,' should I kill him, Messenger of Allah, after he has said that?"The Messenger of Allah ﷺ replied, "Do not kill him."He said, "Messenger of Allah, but he cut off one of my hands, and only said that after cutting it off!"The Messenger of Allah ﷺ said, "Do not kill him. If you kill him, he is in the position you were in before you killed him, and you are in the position he was in before he spoke the words he said."

Azami 6821

Sahih

عن المقداد بن عمرو الكندي- وكان حليفا لبني زهرة، وكان ممن شهد بدرا مع رسول الله ﷺ

- أنه قال لرسول الله ﷺ: أرأيت إن لقيت رجلا من الكفار فاقتتلنا، فضرب إحدى يدي بالسيف فقطعها، ثم لاذ مني بشجرة فقال: أسلمت الله، أأقتله يا رسول الله بعد أن قالها؟ فقال رسول الله ﷺ: لا تقتله فقال يا رسول الله، إنه قطع إحدى يدي، ثم قال ذلك بعد ما قطعها؟ فقال رسول الله ﷺ: لا تقتله، فإن قتلته فإنه بمنزلتك قبل أن تقتله، وإنك بمنزلته قبل أن يقول كلمته التي قال.

الأعظمي 6821صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Retaliation and crimes
Chapter
Prohibition of protected blood
Section
Stern prohibition of killing a disbeliever if he accepts Islam and pronounces the two testimonies of faith
Numbering
Jami al-Kamil 6821 (2nd edition)
Azami 6821