Costly sacrifice is the surest sign of true faith

"Just as we cannot have Christian ethics without Christian beliefs, so we do not genuinely believe if we are not living our faith.  In The Religious Affections, Jonathan Edwards observed that costly sacrifice is the surest sign of true faith.  He wrote:

'Passing affections easily produce words; and words are cheap; and godliness is more easily feigned in words than in actions.  Christian practice is a costly, laborious thing...  Hypocrites may much more easily be brought to talk like saints, than to act like saints.'

"Hypocrites seek maximum press with minimum effort.  They shy away from anything that demands a price. If you want to know whether your faith is genuine or not, consider how much it costs you.  Do you resist temptation? Love the people you are with? Give your best to others?  Those who believe in Christ - who have placed their whole weight on the promises of gospel - will naturally look for ways to share his love."

Michael E. Wittmer: Don't Stop Believing, p. 174.