'It makes no difference
It makes no difference what a man believes, or what doctrines he holds
" It makes no difference what a man believes, or what doctrines he holds — it is only his conduct that counts."
That is the way some people talk, as they sneer at Bible doctrines.
But it does matter what one believes. Wrong believing leads to wrong living. The heathen worships a god conceived of as lustful, cruel, and unholy.
The Christian worships a God, who is revealed as holy, righteous, pure, and good, and becomes holy, righteous, pure, and good.
Beliefs shape our lives. It is important, therefore, that we know the truths about the character and will of Christ, as our conception of Christ will imprint itself upon our life .
"Let the word of Christ dwell in you richly" Colossians 3:16
"He must hold firmly to the trustworthy message as it has been taught, so that he can encourage others by sound doctrine and refute those who oppose it." Titus 1:9
"You must teach what is in accord with sound doctrine." Titus 2:1