Martin Luther

Search and examine your own heart thoroughly and you will find whether or not it
clings to God alone. Do you have the kind of heart that expects from him nothing
but good, especially in distress and want, and renounces and forsakes all that is
not God? Then you have the one true God. On the contrary, does your heart cling
to something else, from which it hopes to receive more good and help than from
God, and does it flee not to him but from him when things go wrong? Then you
have an idol, another god.

--Martin Luther