What does the sheriff mean when he tells atticus let the dead bury the dead?

Believers take care of Believers

Matt 22:32

'I am the God of Abraham, the God of Isaac, and the God of Jacob God is not the God of the dead, but of the living."

John 3:16

For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life