A believer will remain in the spaciousness of his religion as long as he does not shed inviolable blood

The Prophet (may Allah's peace and blessings be upon him) informed that a believer remains in the spaciousness and vastness of his righteous deeds, with hope for Allah's mercy, forgiveness, and pardon, until he kills someone unlawfully, whereupon his deeds become constricted, because they cannot compensate for the grave sin and guilt of murder.

1. The gravity of killing unjustly and intentional murder, as it takes the believer from the spaciousness of the religion into constriction.
2. There are four categories of prohibited blood: 1. The blood of a Muslim, which is the most severe. 2. The blood of a Dhimmi, which refers to the Jews and Christians who live in an Islamic state under their own religion, paying Jizyah (protection tax) and adhering to the laws of Islam. 3. The blood of a Mu‘āhid, which refers to the disbelievers in their own lands with whom we have a peace treaty, meaning they do not fight us and we do not fight them. 4. The blood of a Musta’min, which refers to a combatant disbeliever who does not have a covenant or treaty with us, but we have granted him protection for a specific period, allowing him to enter the Muslim lands with permission from the ruler or an authorized representative.

صحيح البخاري (9/ 2) (6862). إرشاد الساري لشرح صحيح البخاري (10/ 41). تطريز رياض الصالحين (ص: 171).