1 Peter 3:15  
But sanctify the Lord God in your hearts, and always be ready to give a defense to everyone who asks you a reason for the hope that is in you, with meekness and fear; 

Psalm 14:1
The fool has said in his heart,"There is no God." They are corrupt, They have done abominable works, There is none who does good. 
Psalm 51:1
The fool has said in his heart,"There is no God." They are corrupt, and have done abominable iniquity; There is none who does good.