1270 – Ibn Masʿūd (may Allah be pleased with him) reported: “I asked the Messenger of Allah ﷺ, ‘Which sin is the greatest?’ He replied, ‘To set up a rival to Allah, though He alone created you.’ I said, ‘Then what comes next?’ He answered, ‘That you kill your child for fear that he will share your food with you.’ I asked, ‘Then what?’ He said, ‘That you commit adultery with your neighbour’s wife.’” Agreed upon. (1)

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Vocabulary of the ḥadīth
• niddan: with kasrah on the nūn and a doubled dāl; it means an equal, counterpart, or partner.
• tuzānī ḥalīlah: al-ḥalīlah is one’s wife; the verb “tuzānī” (“you commit adultery with”) implies her consent. Doing so is a serious betrayal of the neighbour whose rights must be honoured.

Points derived from the ḥadīth
1 – The report mentions three of the destructive sins:
First: “to set up a rival,” that is, major shirk (polytheism), the gravest of all sins and the worst act of disobedience. It is not forgiven unless the person repents by entering Islam; whoever dies upon shirk will dwell eternally in the Fire.
Allah, Exalted is He, says, “Indeed, Allah does not forgive that partners be associated with Him.” ⦗4:48⦘
He also says, “Those who disbelieve from the People of the Scripture and the idolaters will be in the Fire of Hell, abiding therein forever; they are the worst of all creatures.” ⦗98:6⦘
There are many other Qurʾanic verses and prophetic reports on this issue.
Second: “that you kill your child for fear that he will share your food with you”; taking a life that Allah has made inviolable