Question: It is said that Riddah (apostasy) may be committed either by words or actions. I hope that you briefly clarify for me the verbal, practical and doctrinal forms of Riddah.
Answer: Riddah is reverting to Kufr (disbelief) after accepting Islaam. It may be by word, action, erroneous belief or doubt. Consequently, whoever associates other partners with Allaah; denies His Lordship, His Oneness, one of His Attributes or some of His Books or Messengers… read more here.