A man said, "O Allah's Messenger (ﷺ)! Which sin is the biggest in Allah's Sight?" The Prophet (ﷺ) said, "To set up rivals unto Allah though He Alone created you." That man said, "What is next?" The Prophet (ﷺ) said, "To kill your son lest he should share your food with you.'' The man said, "What is next?" The Prophet said, "To commit illegal sexual intercourse with the wife of your neighbor." Then Allah revealed in confirmation of that: "And those who invoke not with Allah any other god, nor kill such life as Allah has made sacred except for just cause, nor commit illegal sexual intercourse and whoever does this shall receive the punishment..... (25.68)
Oneness, Uniqueness of Allah (Tawheed)
Sahih al-Bukhari 7532
The Primacy of Shirk in Major Sins
The Prophet's response establishes shirk (associating partners with Allah) as the gravest sin, for it corrupts the very foundation of faith—Tawheed. This is the ultimate injustice, as it directs worship to other than the One deserving of it.
Allah alone is the Creator, Sustainer, and the only true object of worship. To set up rivals to Him is to deny His unique rights and attributes, undermining the purpose of creation itself.
The Severity of Murder and Adultery
Killing one's child out of fear of poverty demonstrates extreme distrust in Allah's provision. It combines the violation of the sanctity of life with weak faith in divine decree.
Adultery with a neighbor's wife breaches multiple trusts: the sanctity of marriage, the rights of the neighbor, and the honor of families. It corrupts lineages and disrupts social harmony.
Quranic Confirmation of the Prophetic Teaching
Allah revealed Surah Al-Furqan (25:68) affirming these three major sins: shirk, unjust killing, and adultery. The verse connects these prohibitions, showing they are violations of Allah's limits that warrant severe punishment.
The divine confirmation underscores the eternal validity of the Prophet's teachings and the consistency between revelation and prophetic guidance.