'Sincerity' in the Bible

Therefore, let us celebrate the feast, not with old leaven, nor with leaven of vice and malice and wickedness, but with the unleavened bread of sincerity and [untainted] truth.

This is our [reason for] proud confidence: our conscience testifies that we have conducted ourselves in the world [in general], and especially toward you, with pure motives and godly sincerity, not in human wisdom, but in the grace of God [that is, His gracious lovingkindness that leads people to Christ and spiritual maturity].

For we are not like many, [acting like merchants] peddling God’s word [shortchanging and adulterating God’s message]; but from pure [uncompromised] motives, as [commissioned and sent] from God, we speak [His message] in Christ in the sight of God.

I am not saying this as a command [to dictate to you], but to prove, by [pointing out] the enthusiasm of others, the sincerity of your love as well.

And we desire for each one of you to show the same diligence [all the way through] so as to realize and enjoy the full assurance of hope until the end,

Little children (believers, dear ones), let us not love [merely in theory] with word or with tongue [giving lip service to compassion], but in action and in truth [in practice and in sincerity, because practical acts of love are more than words].

Grace, mercy, and peace (inner calm, a sense of spiritual well-being) will be with us, from God the Father and from Jesus Christ, the Father’s Son, in truth and love.

For I was greatly pleased when [some of the] brothers came [from time to time] and testified to your [faithfulness to the] truth [of the gospel message], that is, how you are walking in truth.