“We were sitting with the Prophet (ﷺ) and he was narrating to us and reminding us, when a man came and spoke privately to him. He said: ‘Take him away and kill him.’ When the man turned away, the Messenger of Allah (ﷺ) called him back and said: ‘Do you bear witness that none has the right to be worshiped but Allah?’ He said, ‘Yes.’ He said: ‘Then go and let him go, for I have been commanded to fight the people until they say: La ilaha illallah, then if they do that, their blood and wealth are forbidden to me.’”
Sunan Ibn Majah Book 36, Hadith 3
← Previous Hadith “I have been commanded to fight the people until they say: La ilaha illallah. If they say: La ilaha illallah, then their blood and wealth are protected from me, except for a right that is due from it, and their reckoning will be with Allah.”

Sunan Ibn Majah Book 36, Hadith 2 Next Hadith → “Nafi’ bin Azraq and his companions came and said: ‘You are doomed, O ‘Imran!’ He (‘Imran) said: ‘I am not doomed.’ They said: ‘Yes you are.’ I said: ‘Why am I doomed?’ They said: ‘Allah says: “And fight them until there is no more Fitnah (disbelief and polytheism, i.e., worshipping others besides Allah), and the religion (worship) will be all for Allah Alone.” He said: ‘We fought them until they were defeated and the religion was all for Allah Alone. If you wish, I will tell you a Hadith that I heard from the Messenger of Allah (ﷺ).’ They said: ‘Did you (really) hear it from the Messenger of Allah (ﷺ)?’ He said: ‘Yes. I was with the Messenger of Allah (ﷺ) and he had sent an army of the Muslims to the idolaters. When they met them they fought them fiercely, and they (the idolaters) gave them their shoulders (i.e., turned and fled). A man among my kin attacked an idolator man with a spear, and when he was defeated he said: “I bear witness that none has the right to be worshipped but Allah, I am a Muslim.” But he stabbed him and killed him. He came to the Messenger of Allah (ﷺ) and said: “O Messenger of Allah, I am doomed.” He said “What is it that you have done?” one or two times. He told him what he had done and the Messenger of Allah (ﷺ) said to him: “Why didn’t you cut open his belly and find out what was in his heart?” He said: “O Messenger of Allah, I wish I had cut open his belly and could have known what was in his heart.” He said: “You did not accept what he said, and you could not have known what was in his heart!” The Messenger of Allah (ﷺ) remained silent concerning him (that man), and a short while later he died. We buried him, but the following morning he was on the surface of the earth. They said: “Perhaps an enemy of his disinterred him.” So we buried him (again) and told our slaves to stand guard. But the following morning he was on the surface of the earth again then we said: ‘Perhaps the slaves dozed off.’ So we buried him (again) and stood guard ourselves, but the following morning he was on the surface of the earth (again). So we threw him into one of these mountain passes.’”

Sunan Ibn Majah Book 36, Hadith 4