The Book of Faith - Sahih Muslim 86a

I asked the Messenger of Allah (ﷺ): Which sin is the gravest in the eye of Allah? He (the Holy Prophet) replied: That you associate a partner with Allah (despite the fact) that He has created you. He (the reporter) said: I told him (the, Holy Prophet): Verily it is indeed grave. He (the reporter) said: I asked him what the next (gravest sin) was. He (the Holy Prophet) replied: That you kill your child out of fear that he shall join you in food. He (the reporter) said: I asked (him) what the next (gravest sin) was. He (the Holy Prophet) observed: Then (the next gravest sin) is that you commit adultery with the wife of your neighbour.

Commentary on Shirk (Associating Partners with Allah)

The Prophet (ﷺ) identifies shirk as the gravest sin because it violates the fundamental purpose of creation - to worship Allah alone. This constitutes the ultimate injustice against the Creator's rights, denying His exclusive divinity despite His being the sole source of existence and sustenance.

Scholars explain that shirk nullifies all good deeds and earns eternal punishment if one dies without repenting. The gravity lies in directing worship - which belongs exclusively to Allah - toward created beings, thus equating the creation with the Creator in His most unique attribute.

Commentary on Killing Children

This refers to the pre-Islamic practice of burying daughters alive due to poverty or fear of shame. Scholars emphasize this sin's severity as it combines multiple transgressions: murder, betrayal of parental trust, and distrust in Allah's provision.

Ibn Hajar notes that this demonstrates extreme lack of trust in Allah's sustenance, as the killer assumes Allah will not provide for the child. It also represents the ultimate violation of the sanctity of life which Allah has made sacred.

Commentary on Adultery with Neighbor's Wife

This specific formulation highlights multiple aggravating factors: adultery itself violates chastity laws, while targeting a neighbor's wife compounds the sin through betrayal of trust and violation of neighborhood rights.

Al-Nawawi explains that neighbors enjoy special rights in Islam, and violating their honor represents a double transgression. The proximity makes the sin more damaging to social fabric and family structures, explaining its placement among the gravest sins.

Scholarly Observations

The hierarchy presented demonstrates Islam's comprehensive moral framework, addressing sins against Allah, family, and society. This ordering reflects the Islamic principle of prioritizing rights: first Allah's rights, then human rights beginning with the most vulnerable.

The hadith's format of progressive questioning shows the Companion's desire to understand Islamic ethics systematically, establishing a model for seeking religious knowledge through proper channels and with due reverence.