belonging to the Muslims, and any other injury they inflict upon them, is not subject to restitution. In other words, if a non-Muslim damages Muslim property or even takes a life, and then embraces Islam, he is not held financially liable, for Islam effaces everything that came before it.
The second incident is as follows: the Prophet ﷺ dispatched Usama ibn Zayd at the head of a detachment to al-Hurqa of the tribe of Juhaynah. When the force reached the tribe and fell upon them, one of the idolaters fled. Usama and an Ansari pursued him, intent on killing him. Just as they caught up with him, the man declared, “There is no deity but Allah.” The Ansari—being more versed in the religion than Usama—refrained and let him go when he heard the declaration, whereas Usama struck him down.
Upon their return to Medina, news of the incident reached the Prophet ﷺ. He said to Usama, “Did you kill him after he said, ‘There is no deity but Allah’?” Usama replied, “Yes, O Messenger of Allah, for he only uttered it to seek protection from being killed.” The Prophet repeated, “Did you kill him after he said, ‘There is no deity but Allah’?” Usama answered, “Yes, he said it merely to save his life.” The Prophet kept repeating the question until, in one version narrated by Muslim, he asked, “What will you do with ‘There is no deity but Allah’ when it confronts you on the Day of Resurrection?”
Usama (may Allah be pleased with him) later said, “I wished I had not embraced Islam before that day,” for had he been a disbeliever who then accepted Islam, Allah would have pardoned him, but now he had committed this deed while already a Muslim, a matter that weighed heavily upon him.
Still, the Messenger of Allah ﷺ kept repeating, “Did you kill him after he said, ‘There is no deity but Allah’? What will you do with ‘There is no deity but Allah’ when it confronts you on the Day of Resurrection?”—despite the strong likelihood, evident to Usama, that the man had uttered it solely to escape death. Yet once he pronounces “There is no deity but Allah,” the matter is settled: we must desist from harming him, and his life and property become inviolate. Whether he said it out of fear or hypocrisy, his reckoning is with Allah.