What did Allah's Apostle (saw) say is the biggest sin in the Sight of Allah?
 Narrated `Abdullah:                     I or somebody, asked Allah's Apostle "Which is the biggest sin in the Sight of Allah?" He said, "That you set up a rival (in worship) to Allah though He Alone created you." I asked, "What is next?" He said, "Then, that you kill your son, being afraid that he may share your meals with you." I asked, "What is next?" He said, "That you commit illegal sexual intercourse with the wife of your neighbor." Then the following Verse was revealed to confirm the statement of Allah's Apostle: "Those who invoke not with Allah, any other god, nor kill life as Allah has forbidden except for just cause, nor commit illegal sexual intercourse." (25.68)