'Sincerity' in the Bible

"So now, revere Yahweh and serve him in sincerity and faithfulness; remove the gods that your ancestors served beyond the river and in Egypt, and serve Yahweh.

"So then, if you have acted in good faith and sincerity in making Abimelech king, and if you have dealt well with Jerub-Baal and his house, and have dealt with him {according to his accomplishments}--

if you have acted in good faith and sincerity with Jerub-Baal and his house this day, then rejoice in Abimelech, and let him also rejoice in you.

if [it is] one who exhorts, by exhortation; one who gives, with sincerity; one who leads, with diligence; one who shows mercy, with cheerfulness.

So then, let us celebrate the feast, not with the old leaven or with the leaven of wickedness and sinfulness, but with the unleavened bread of sincerity and truth.

But I am afraid lest somehow, as the serpent deceived Eve by his craftiness, your minds may be led astray from the sincerity and the purity of [devotion] to Christ.

Slaves, obey your earthly masters with fear and trembling, in the sincerity of your heart, as to Christ,

Slaves, obey your {human} masters in everything, not {while being watched}, as people pleasers, but with sincerity of heart, fearing the Lord.