Albert Barnes Commentary Titus 2:9

"[Exhort] servants to be in subjection to their own masters, [and] to be well-pleasing [to them] in all things; not gainsaying;" — Titus 2:9 (ASV)

Exhort servants to be obedient to their own masters. See this explained in Ephesians 6:5 and following, and 1 Timothy 6:1–4.

And to please them well in all things. That is, so far as they lawfully may, or in those things which are not contrary to the will of God. (Compare to Ephesians 6:6.) It should be an object for one who is a servant to meet the approbation of his master, as long as this relation continues. This rule would not, however, go to the extent of requiring him to please his master in doing anything that is contrary to the law of God, or that is morally wrong.

Not answering again. (The marginal reading is gainsaying.) Not contradicting or not disobeying. They were to do what the master required, if it did not interfere with the rights of conscience, without attempting to argue the matter—without disputing with the master—and without advancing their own opinions. Where this relation exists, no one can doubt that this is a proper frame of mind for a servant.

It may be observed, however, that all that is said here would be equally appropriate, whether the servitude was voluntary or involuntary. A man who voluntarily becomes a servant binds himself to obey his master cheerfully and quietly, without gainsaying, and without attempting to reason with him or propound his own opinions, even though they may be much wiser than those of his employer. He makes a contract to obey his master, not to reason with him, or to instruct him.