External Christianity is not enough.

The gospel is not a doctrine of the tongue, but of life.  I cannot be grasped by reason and memory only, but it is fully understood when it possesses the whole heart.

Let nominal Christians cease from insulting God by boasting themselves to be what they are not, and let them show themselves disciples not unworthy of Christ, their master.

We must assign first place to the knowledge of our religion, for that is the beginning of our salvation.

But our religion will be unprofitable if it does not change our heart, pervade our manner, and transform us into new creatures.
(GBTCL, 21)