Messenger of Allah, which offence is the most grievous in the eye of Allah? He (the Holy Prophet) replied: That you associate a partner with Allah (despite the fact) that He created you. He (the man) said: What next? He (the Holy Prophet) replied: That you kill your child out of fear that he would join you in food. He (the inquirer) said (again): What next? He (the Holy Prophet) replied: That you commit adultery with the wife of your neighbour. And the Almighty and Exalted Lord testified it (with this verse): All those who call not unto another god along with Allah, and slay not any soul which Allah has forbidden, except in the cause of justice, nor commit fornication, and he who does this shall meet a requital of sin (xxv. 68).
The Book of Faith - Sahih Muslim 86b
This narration from the Messenger of Allah (peace be upon him) establishes the hierarchy of major sins, with shirk (associating partners with Allah) being the gravest offence. The Prophet's response demonstrates that sins against Allah's rights take precedence over sins against creation.
Commentary on Shirk (Associating Partners)
The foremost sin is shirk because it constitutes rejection of tawhid (divine unity), the fundamental purpose of creation. Allah emphasizes "He created you" to remind that the Creator alone deserves worship. This is the ultimate injustice, attributing divine qualities to created beings.
Commentary on Killing Children
The second grave sin mentioned is killing children due to poverty fears, known as wa'd al-banat in pre-Islamic Arabia. This violates the sanctity of life Allah bestowed and demonstrates distrust in divine provision. The Prophet highlighted this specific historical context while establishing the general prohibition of unlawful killing.
Commentary on Adultery with Neighbor's Wife
Adultery with a neighbor's wife compounds multiple transgressions: violating marital sanctity, betraying community trust, and damaging social fabric. The specification "neighbor's wife" emphasizes the additional sin of breaching neighborhood rights, which Islam strongly protects.
Quranic Corroboration
The Prophet's teaching is confirmed by Surah al-Furqan (25:68), demonstrating the harmony between Quran and Sunnah. The verse mentions the same three major sins in similar order, showing their severity in divine judgment and the severe punishment awaiting those who commit them without repentance.