Mukhtasar Muslim

Narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him), he said: A man asked, "O Messenger of Allah! Which sin is the greatest in the sight of Allah?" The Prophet (peace and blessings be upon him) replied: "That you associate a partner with Allah while He alone created you." He asked, "Then which (sin is greatest)?" The Prophet (peace and blessings be upon him) replied: "That you kill your child out of fear that he will eat with you." He asked, "Then which (sin is greatest)?" The Prophet (peace and blessings be upon him) replied: "That you commit adultery with your neighbor's wife." Then Allah the Exalted revealed this verse in confirmation of this hadith: "And those who do not invoke any other god along with Allah, nor kill such life as Allah has forbidden except for just cause, nor commit adultery—and whoever does this shall meet the penalty." (Surah Al-Furqan: 68).