I have wondered at the use of the word slave, a word that typically has universally negative connotations. Isn't a "faithful" slave something of an oxymoron? Does a slave have a choice whether to be faithful or not? Don't they operate under threat of physical coercion for any transgression or for not following the master's orders? I wouldn't see much value or fidelity in a slave carrying out orders, I would see more in the way of self-preservation in those acts. The faithfulness of a partner or an employee would certainly seem to be more meaningful than one's chattel property.
All this talk of being slaves to God seems a bit, off, to say the least. Is that really the relationship that we would seek or want to foster?
In a broader sense I have always wondered why the bible was largely silent on the topic of slavery, something today's society has condemned as evil.