Faith is an intellectual elective you invoke at will no sin involve.

Article by  John Piper

Founder & Teacher, desiringGod.org

People from the time of John Chrysostom (347–407) have tried to limit the meaning of Paul’s words in Romans 14:23, “Whatever does not proceed from faith is sin.” Chrysostom cautions, “Now all these things have been spoken by Paul of the subject in hand, not of everything.” Leon Morris follows this limitation and says,

Whatever be the truth of actions done before one becomes a believer, Paul is not discussing them here. His concern is with the believer who sometimes does things that are not motivated by faith.  john