Fear the sins that you commit in secret, because the Witness of those sins is the Judge Himself!
The disease of the heart is worse than the disease of the body.
Vanity prevents improvement
Always consider your intellect to be lacking; otherwise too much faith in it surely leads to error.
Dislike in yourself what you dislike in others.
Knowledge is of two kinds: that which is absorbed and that which is heard. And that which is heard does not profit if it is not absorbed.