'Sincerity' in the Bible

For our reason for confidence is this: the testimony of our conscience, that with pure motives and sincerity which are from God -- not by human wisdom but by the grace of God -- we conducted ourselves in the world, and all the more toward you.

For we are not like so many others, hucksters who peddle the word of God for profit, but we are speaking in Christ before God as persons of sincerity, as persons sent from God.