These prohibitions open with Allah’s words, “that you associate nothing with Him,” indicating that shirk is the gravest act He has forbidden.

In Sūrat al-Isrāʾ, Allah the Exalted says: “Do not set up alongside Allah any other deity, lest you sit down rebuked and forsaken” (al-Isrāʾ 17:22). He begins the passage with a ban on shirk and ends it with the same prohibition, saying: “And do not set up alongside Allah any other deity, or you will be thrown into Hell, blamed and rejected” (al-Isrāʾ 17:39). This proves that shirk is the greatest thing Allah has forbidden—exactly as the Shaykh stated: “The most serious prohibition is shirk.”

In a sound hadith the Prophet (peace and blessings be upon him) was asked, “Which sin is the greatest?” He answered, “That you set up a rival to Allah while He created you.” He was asked, “Then which?” He said, “That you kill your child for fear he will share your food.” He was asked again, “Then which?” He said, “That you commit adultery with your neighbor’s wife.”

Allah confirmed this by revealing: “Those who do not call upon another god alongside Allah, nor kill a soul that Allah has made sacred except by right, nor commit adultery—and whoever does that shall meet a penalty” (al-Furqān 25:68). Thus, the verse begins by mentioning shirk.