Although it's not very socially acceptable today, the Bible is full of stories about slaves. There are servants as far back, at least, as Abraham, who took one with him when he and Isaac went to Mount Moriah. Joseph was sold into slavery. Israel herself became slaves in Egypt. The nations that she didn't destroy in the Promised Land became her slaves. Israel was brought into slavery again in Babylon. Even in the New Testament, we see references to slaves and slavery - one of the letters that we have is from Paul to the owner of a certain slave, Philemon, lauding the slave's tremendous help.
For most of us who live in a post-slave society (we cannot say a post-slave world, since slavery still exists and, to be honest, we still live in a society of sex slavery, so we cannot even say this really about ourselves), this is hardly fathomable. How atrocious! we say. How terrible! Slavery! We just shake our heads.
And it's true that even in the Bible, slavery is often talked about in negative terms. No one wants to be a slave. Joseph didn't want to be a slave; his brothers sold him into it. Israel didn't want to be slaves in Egypt; that's not how they started out there. The other nations weren't keen on the idea of becoming Israel's slaves; it was, however, better than the alternative (being claimed for the Lord by the sword - i.e. dying). In many cases, their slavery wasn't even part of God's agenda; it was a trick to save themselves.
But despite this, we also see that slaves have tremendous power in the Scriptures, for better and for worse.
This is important because Paul says that we should be slaves to Christ. And most of us, in our postmodern, individualistic mindset, really struggle with this. Me? A slave? Forget it! I do what I want when I want and nobody can tell me what to do. Not even Christ Himself. (And even if we are not so bold as to say this out loud in so many words, it is the way we're living, as though we have no master at all.)
Yet as is also true what we find in the other Biblical wisdom - we're all slaves to something. If we're not serving Christ, we're serving something else. We're slaves to Christ, or we're slaves to sin. We're slaves to Christ, or we're slaves to money. Even as far back as the Old Testament, Joshua declared, "Choose for yourselves this day who you will serve, whether the Gods of your forefathers or the gods of the people in whose land you are living." Notice that he doesn't given an option for not serving any god at all.
It's not possible.
We're all slaves to something. We are not our own. And that's why it's important to look at some of the things that the Bible story teaches us about slaves, about the power that they hold (for better or for worse) and what kind of impact we can have on the world, depending on whose house we choose to live in.