Bible Verses About Sincerity: Servants must render honest service

Servants, be obedient to those who according to the flesh are your masters, with fear and trembling, in singleness of your heart, as to Messiah;

not in the way of service only when eyes are on you, as men pleasers; but as servants of Messiah, doing the will of God from the heart;

with good will doing service, as to the Lord, and not to men;