Hakikat Kitabevi Publications No: 10 answer to an enemy of islam

ilâha ill-Allâh’, should not be called a kâfir on account of his
sinning! He who calls him a kâfir will become a kâfir himself.” A
person who will not enter Hell because of his correct belief may
enter Hell because of the sins he commits. If he is sâlih (true,
pious, devoted), that is, if he repents for his sins or attains
forgiveness or shafâ’a, he will never enter Hell. Because a person
who denies a belief or a deed which has been communicated
unanimously and is indispensable, that is, known even by the
ignorant, will become a disbeliever or a renegade, he is not called
a believer in “Lâ ilâha ill-Allah” or a man of the qibla or a holder
of bid’a, even if he says “Lâ ilâha ill-Allah,” does all kinds of
’ibâdât and avoids all kinds of sins.
Question: “Our Prophet (sall-Allâhu ’alaihi wa sallam)
declared, 
‘All bid’as are heresy.’ But the scholars of fiqh said that
some bid’as were mubâh (permitted), some were mustahab and
some were wâjib. How can these two statements be reconciled?”
Answer: The word ‘bid’a’ has two meanings. The first is its
lexical meaning, which is general. In this sense, any kind of
innovation, whether in customs or in ’ibâdât is called bid’a.
Customs are actions for which thawâb is not expected and which
are done for worldly advantages. But ’ibâdât are done for gaining
thawâb in the hereafter. Lexically, bid’a means all kinds of
innovations introduced after 
as-sadr al-awwal, which covers the
times of the Salaf as-sâlihîn, that is, the Sahâbat al-kirâm, the
Tâbi’în, and the Taba’ at-Tâbi’în. Things introduced in their times
are not bid’as. Bid’as are the innovations introduced after the
Tâbi’în and the Taba’ at-Tâbi’în.
The second meaning of the word ‘bid’a’ is the innovations in
the religion that are introduced after as-sadr al-awwal. These
changes are either in belief or in ’ibâdât. To invent a new ’ibâda
or to put some addition or deletion in an ’ibâda is a