Proverbs 4:23
Keep your heart with all diligence; for out of it are the issues of life.

Titus 1:15,16
15. Unto the pure all things are pure: but unto them that are defiled and unbelieving is nothing pure; but even their mind and conscience are defiled.
16. They profess that they know GOD; but in works they deny Him, being abominable, and disobedient, and unto every good work reprobate.