Al-Miqdad bin Al-Aswad (May Allah be pleased with him) reported:
I said, "Tell me, O Messenger of Allah, if I meet an infidel, and we fight together, and he cuts off my hands with his sword, then hides from me behind a tree and (then) says he has submitted himself to Allah. Shall I kill him after he has said it?" He ﷺ replied, "Do not kill him." I submitted, "But O Messenger of Allah, he cut off one of my hands and only then he said it." Messenger of Allah ﷺ then replied, "Do not kill him, for if you do so, he will be in the position in which you were before you killed him (i.e., he will be considered a Muslim and thus his life will be inviolable), and you will be in the position in which he was before he made his testimony (i.e., your life will not be inviolable, for his heirs can ask for Qisas)".

[Al-Bukhari and Muslim].

وعن أبي المقداد بن الأسود، رضي الله عنه ، قال: قلت لرسول الله ﷺ : أرأيت إن لقيت رجلاً من الكفار، فاقتتلنا، فضرب إحدى يدى بالسيف، فقطعها، ثم لاذ منى بشجرة، فقال أسلمت لله، أأقتله يارسول الله بعد أن قالها؟ فقال: "لا تقتله، فإن قتلته، فإنه بمنزلتك قبل أن تقتله، وإنك بمنزلته قبل أن يقول كلمته التى قال" ((متفق عليه)) . (1)