Narrated Usama bin Zaid: Allah's Apostle sent us towards Al-Huruqa, and in the morning we attacked them and defeated them. I and an Ansari man followed a man from among them and when we took him over, he said, "La ilaha illal-Lah." On hearing that, the Ansari man stopped, but I killed him by stabbing him with my spear. When we returned, the Prophet came to know about that and he said, "O Usama! Did you kill him after he had said "La ilaha ilal-Lah?" I said, "But he said so only to save himself." The Prophet kept on repeating that so often that I wished I had not embraced Islam before that day.

Narrated Usama bin Zaid bin Haritha: Allah's Apostle sent us (to fight) against Al-Huraqa (one of the sub-tribes) of Juhaina. We reached those people in the morning and defeated them. A man from the Ansar and I chased one of their men and when we attacked him, he said, "None has the right to be worshipped but Allah." The Ansari refrained from killing him but I stabbed him with my spear till I killed him. When we reached (Medina), this news reached the Prophet. He said to me, "O Usama! You killed him after he had said, 'None has the right to be worshipped but Allah?"' I said, "O Allah's Apostle! He said so in order to save himself." The Prophet said, "You killed him after he had said, 'None has the right to be worshipped but Allah." The Prophet kept on repeating that statement till I wished I had not been a Muslim before that day.