The following is from Spurgeon's sermon,
"Every day Usefulness" #855.  John 1:42.

People who become active in church work
before they have first believed in Christ,
are very apt to remain without faith,
resting content with the general
reputation which they have gained.

O dear friends, beware of this.

In this day hypocrisy is so common, self
deceit is so easy, that I would not have
you place yourselves where those vices
become almost inevitable.  If a man
voluntarily puts himself where it is taken
for granted that he is godly, his next
step will be to mimic godliness, and
by and by he will flatter himself into
the belief that he really possesses that
which he so successfully imitates.

Beware of a religion which is
not true; it is worse than none.

Beware of a form of godliness which is not
supported by the fervor of your heart and soul.

This age of shams presents but few assistances
to self-examination, hence am I the more earnest
that every one of us should deliberately ask himself,
"Am I a follower of Christ myself? Am I washed in
his blood? Am I renewed by his Spirit?"  If not, my
first business is on my knees in prayer; my first
occupation should be in my closet, confessing my
sin and seeking pardon through the atoning sacrifice.