Difference between voluntary manslaughter of a believer and a Muslim

Q 1: Allah (Exalted be He) says: And whoever kills a believer intentionally, his recompense is Hell to abide therein Allah (Exalted be He) states that Fire is the punishment for a person who kills a believer, not a Muslim. Would a person who kills a Muslim also receive the same punishment?

A: Whoever kills a Muslim, their punishment will be the Fire. If the inward aspects of the person being killed are in agreement with their outward aspects, they are regarded as believers as well; and their killers deserve the punishment stated in the Ayah (Qur'anic verse) mentioned above. If the inward aspects of the person being killed are not in agreement with their outward aspects, we should deal with them according to their outward aspects and we have no right to probe into their inward aspects. As a result, their blood is protected by Islam and no one has the right to transgress it. This is because it was authentically reported from Abu Hurayrah (may Allah be pleased with him) that the Prophet (peace be upon him) said: "I have been ordered to fight against the people until they testify that none has the right to be worshipped but Allah and that Muhammad (peace be upon him) is Allah's Messenger. If they do so, they will save their lives and property from me, unless (they do acts that are punishable) in accordance with Islam, and their reckoning will be with Allah." (Related by Al-Bukhari, Muslim, and Ahl-ul-Sunan (authors of Hadith compilations classified by jurisprudential themes)) It was authentically reported from Usamah ibn Zayd (may Allah be pleased with them) that he said: "We were sent by Allah's Messenger (peace be upon him) to Al-Hurqah where we attacked its people early in the morning and defeated them. A man from Al-Ansar (Helpers, inhabitants of Madinah who supported the Prophet) and me chased a person from those people. When we caught him, he testified that there is no god but Allah. As a result, the man from Al-Ansar stopped fighting that man, but I stabbed him to death with my spear. When (Part No. 21; Page No. 224) we returned to the Prophet (peace be upon him) and he was informed of what happened, he said, "O Usamah! Did you kill him after he had testified that there is no god but Allah?" I said, "He said so to protect himself from us." The Prophet (peace be upon him) kept on uttering the sentence mentioned above until I wished I had not embraced Islam before that day." (Related by Al-Bukhari and Muslim) The Prophet (peace be upon him) did not regard the assumption of Usamah (may Allah be pleased with him) - that the person he killed was not truthful with regard to his Iman (Faith) - as a reason for not stressing that no one has the right to strip a person of Iman until Usamah felt really guilty for what he had done. Usamah said, "I wished I had not embraced Islam before that day." This proves that the worldly judgments apply to the outward aspects of people. Accordingly, whoever kills a Muslim intentionally is sinful and commits a major sin and deserves the Fire as a punishment unless this is done for one of the three lawful reasons mentioned by the Prophet (peace be upon him) when he said: "The blood of a Muslim is not lawful (to shed) except in three (cases): Qisas (just retaliation) for murder, a married person who commits adultery, and a person who renounces his Din (religion of Islam) and splits from the Jama`ah (the Muslim main body)." Also, some Nusus (Islamic texts from the Qur’an or the Sunnah) may include the word "believer", but it is intended to refer to both Muslims and believers alike. For example, Allah (Exalted be He) says when describing Kaffarah (expiation): (Part No. 21; Page No. 225)  ...he must set free a believing slave May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.