The secret of living by faith is to stay away from doubts. But what produces doubts? Sin. Sin is anything that contradicts God. It’s born of rebelliousness against His Word. The undisciplined and rebellious hate the works of the light; they hate order and justice. That’s why the Lord Jesus said to the religious hypocrites:

“You are of your father the devil, and the desires of your father you want to do.” (John 8:44)

Whoever wants to remain firm in the faith must keep his conscience clean. And in order to do this, he must sacrifice his fleshly desires.