Musnad Abu Ya'la al-Mawsili 65:4

Ubayd Allah ibn Umar al-Qawariri narrated to us, Abd al-Rahman ibn Mahdi narrated to us, Abd al-Hamid ibn Bahram narrated to me, Shahr ibn Hawshab narrated to us, Jundub ibn Sufyan, a man from Bajilah, narrated to me, saying: I was with the Messenger of Allah (peace be upon him) when a messenger came to him from a military detachment he had sent. He informed him of the victory of Allah, which He granted to his detachment, and of the conquest of Allah, which He opened for them. He said: "O Messenger of Allah, while we were in pursuit of the enemy, and Allah had defeated them, I caught up with a man with a sword. When he sensed that the sword had reached him, he turned while he was running and said, 'I am a Muslim, I am a Muslim.' But I killed him, and he was only, O Prophet of Allah, seeking refuge." He (the Prophet) said: "Why did you not split open his heart to see if he was truthful or a liar?" He said: "If I had split open his heart, would the heart have taught me? Is the heart anything but a piece of flesh?" He said: "Then you killed him; you did not know what was in his heart, nor did you believe his tongue." He said: "O Messenger of Allah, ask forgiveness for me." He said: "I will not ask forgiveness for you." So they buried him, but he appeared on the surface of the earth three times. When his people saw that, they were ashamed and humiliated by what he had encountered, so they carried him and threw him into a ravine among those ravines.