Question: What is the ruling on a person who does not perform any obligatory acts of `Ibaadah (worship) like Salaah (Prayer) even though he is well? He used to do good deeds and avoid evil ones. He says: “Allaah is Forgiving and Merciful. I do no evil deeds and I love doing good.” However, some people also perform Salah and do righteous deeds, but commit sins such as Zinaa (sexual intercourse outside marriage), Ribaa (usury) and drinking Khamr (alcohol or any other intoxicant). What is the ruling on doing so?
Answer: Firstly: Abandoning Salaah is an act of Al-Kufr Al-Akbar (major form of disbelief) even if one does not deny its obligation. This is the most proper viewpoint of scholars. The Prophet (peace be upon him) said: That which differentiates us from the Kuffaar (disbelievers) and hypocrites is our performance of Salaah. He who abandons it, becomes a Kaafir (disbeliever).There are other Ahaadeeth of the same meaning… read more here.