Bible Verses About Sincerity: Servants must render honest service

Servants, be obedient unto them that according to the flesh are your masters, with fear and trembling, in singleness of your heart, as unto Christ;

not in the way of eyeservice, as men-pleasers; but as servants of Christ, doing the will of God from the heart;

with good will doing service, as unto the Lord, and not unto men: