Question: Is establishment of other pillars of Islaam a criterion for the validity of the pillar of Shahaadah (Testimony of Faith)?
Answer: Yes, it is. However, the ruling related to negligence or abandonment of these pillars varies. In certain cases, negligence of these pillars may render a person as being of weak Eemaan (faith). However, all scholars unanimously agree that a person will be considered a Kaafir (disbeliever) if he denies what Allaah (Exalted Be He) has made obligatory or declared as prohibited. Scholars have unanimously agreed that if a person denies the obligatory status of Salaah (Prayer), Sawm (Fasting), or Zakaah (obligatory charity), he will be considered a Kaafir. The same applies to denying the obligatory status of Hajj, the prohibition of Zinaa (adultery), wine-drinking, or the prohibition of showing disrespect to one’s parents… read more here.