The Messenger of Allah ﷺ sent us on a campaign against the Huraqah tribe. We attacked them at dawn and defeated them. A man from the Ansar and I pursued one of their men, and when we overtook him, he said, "There is no god but Allah." The Ansari held back, but I struck him with my spear and killed him.When we returned, news of this reached the Prophet ﷺ, and he said, "Usama, did you kill him after he said, 'There is no god but Allah'?"I replied, "He only said it to seek protection."But he kept repeating the question until I wished I had not become a Muslim before that day.
بعثنا رسول الله ﷺ إلى الحرقة، فصبحنا القوم فهزمناهم ولحقت أنا ورجل من الأنصار رجلا منهم، فلما غشيناه قال: لا إله إلا الله. فكف الأنصاري، فطعنته بر مخي حتى قتلته، فلما قدمنا بلغ النبي ﷺ فقال: يا أسامة أقتلته بعد ما قال لا إله إلا الله قلت: كان متعوذا فما زال يكررها حتى تمنيت أني لم أكن أسلمت قبل ذلك اليوم.
Bukhari reported it in the Book of Military Expeditions (4269) and Muslim in the Book of Faith (96:159), both from the hadith of Hushaym, who said, Husayn Abu Dhubyan told us, he said, I heard Usama bin Zayd bin Haritha narrating, he said, (and he mentioned it), and their wording is identical.Muslim also reported it through another route, from Amash, from Abu Dhubyan, from Usama bin Zayd, who said, The Messenger of Allah ﷺ sent us out on a raiding expedition, and we attacked the Huraqat of Juhayna at dawn. I caught up with a man, and he said, "There is no god but Allah," but I struck him with my spear anyway. Something about that troubled me, so I mentioned it to the Prophet ﷺ. The Messenger of Allah ﷺ said, "Did he say, 'There is no god but Allah,' and you killed him?" I said, "Messenger of Allah, he only said it out of fear of the weapon." He said, "Did you split open his heart to know whether he said it or not?" He kept repeating this to me until I wished I had only just become Muslim that day.Muhammad bin Ishaq also reported it, from Muhammad bin Usama bin Muhammad bin Usama, from his father, from his grandfather Usama bin Zayd, mentioning something similar, and he named the man from the Ansar as Mirdas bin Nahik. Bayhaqi reported it through this route in his Dalail (4/297), except that Ibn Hisham omitted its chain of transmission in his Sirah (2/622-623).