First Ḥadīth

ʿAbd Allāh ibn Masʿūd  relates that the Messenger of Allah ﷺ said: “The blood of a Muslim who bears witness that there is no god but Allah and that I am the Messenger of Allah is not lawful except in one of three cases:

1. the previously-married adulterer,
2. a life for a life,
3. the one who abandons his religion and severs himself from the community.”

Overall meaning
The wise and compassionate Lawgiver is keen to safeguard human life and its security. He therefore surrounded it with protective legislation, deeming the gravest sin after associating partners with Allah to be killing a soul that Allah has made inviolable. Accordingly, He forbade the killing of a Muslim who has affirmed the two testimonies of faith unless that Muslim commits one of three transgressions:

1. A person whom Allah has blessed with lawful intimacy through a valid marriage then commits adultery after having been thus protected.
2. A person who deliberately and unjustly takes the life of another whose blood is sacrosanct. Justice and parity demand that he be dealt with exactly as he dealt with his victim, restoring the right to its owner and deterring predatory souls from further aggression.
3. A person who seeks a path other than that of the believers by apostasizing from Islam after having once embraced its creed. Such a person is executed, for no good remains in someone who tasted the sweetness of faith and then despised and abandoned it.

These three are executed because their elimination safeguards religion, life, and chastity.

Lessons derived from the ḥadīth

1. It is absolutely forbidden to kill a Muslim—male or female, young or old—without legal right.
2. Whoever utters the two testimonies of faith, fulfills what they entail, and abstains from what contradicts them is a Muslim whose life, property, and honor are inviolable; he enjoys the same rights and bears the same duties as all other Muslims.
3. Committing any one of these three offences—let alone all of them—renders the perpetrator liable to the death penalty, whether as disbelief or as a prescribed legal punishment, and thus his blood is without indemnity.
4. The term thayyib refers to the muḥṣan: a free, legally competent person, male or female, who has had lawful intercourse within a valid marriage. If such a person commits adultery, the punishment is stoning to death.
5. Whoever deliberately and unjustly kills a protected soul becomes liable to retaliation (qiṣāṣ), subject to its conditions.