'Sincerity' in the Bible
Now therefore, [reverently] fear the Lord and serve Him in sincerity and in truth; put away the gods which your fathers served on the other side of the [Euphrates] River and in Egypt, and serve the Lord.
My words shall express the uprightness of my heart, and my lips shall speak what they know with utter sincerity.
The Lord rewarded me according to my righteousness (my conscious integrity and sincerity with Him); according to the cleanness of my hands has He recompensed me.
Hear this, O house of Jacob, who are called by the name of Israel and who come forth from the seed of Judah, you who swear allegiance by the name of the Lord and make mention of the God of Israel -- "but not in truth and sincerity, nor in righteousness (rightness and moral and spiritual rectitude in every area and relation) -- "
But in spite of all this, her faithless and treacherous sister Judah did not return to Me in sincerity and with her whole heart, but only in sheer hypocrisy [has she feigned obedience to King Josiah's reforms], says the Lord.
Run to and fro through the streets of Jerusalem, and see now and take notice! Seek in her broad squares to see if you can find a man [as Abraham sought in Sodom], one who does justice, who seeks truth, sincerity, and faithfulness; and I will pardon [Jerusalem -- "for one uncompromisingly righteous person].
Therefore, let us keep the feast, not with old leaven, nor with leaven of vice and malice and wickedness, but with the unleavened [bread] of purity (nobility, honor) and sincerity and [unadulterated] truth.
It is a reason for pride and exultation to which our conscience testifies that we have conducted ourselves in the world [generally] and especially toward you, with devout and pure motives and godly sincerity, not in fleshly wisdom but by the grace of God (the unmerited favor and merciful kindness by which God, exerting His holy influence upon souls, turns them to Christ, and keeps, strengthens, and increases them in Christian virtues).
For we are not, like so many, [like hucksters making a trade of] peddling God's Word [shortchanging and adulterating the divine message]; but like [men] of sincerity and the purest motive, as [commissioned and sent] by God, we speak [His message] in Christ (the Messiah), in the [very] sight and presence of God.
I give this not as an order [to dictate to you], but to prove, by [pointing out] the zeal of others, the sincerity of your [own] love also.
But we do [ strongly and earnestly] desire for each of you to show the same diligence and sincerity [all the way through] in realizing and enjoying the full assurance and development of [your] hope until the end,
Little children, let us not love [merely] in theory or in speech but in deed and in truth (in practice and in sincerity).
Grace (spiritual blessing), mercy, and [soul] peace will be with us, from God the Father and from Jesus Christ (the Messiah), the Father's Son, in all sincerity (truth) and love.