Live as free people, but do not use your freedom as a cover-up for evil; live as God’s slaves (1 Peter 2:16).
The bible is a very curious book in many ways — it often knowingly upholds ideas that seem to be in contradiction. Many of its writers intentionally speak in ways that stretch our minds by asking us to hold two opposites in tension in our minds. Peter does this here: he speaks about living as free people and living as slaves. Evidently these things are compatible, but at first blush it seems terribly strange that they could be.
The critical element here is not merely the concept of slavery and freedom, but slavery and freedom to whom and for whom. To simultaneously be a slave to something and to declare freedom from that thing doesn’t make sense. But here Peter is explaining how our existence has been translated away from slavery under sin (and therefore freedom from it), toward slavery to God (which then actually gives us the freedom we can find nowhere else). So, strange to say, we access true freedom by giving up slavery under one master (sin) for slavery under another one (Jesus).
The idea of being a slave sounds terribly unappealing, quite frankly, no matter who my master might be. But here’s the thing: we choose to be a slave to God. Slaves never chose to be slaves — they were captured in battle and sold, or merely plucked from their homeland and traded like livestock. I don’t know of many people who would willingly choose that. And yet, God does asks us to choose to be his slaves.
So what on earth does it mean to be a slave to God? It really is about relinquishing power over our lives and making ourselves available to do whatever the Master should tell us. When we were under the slavery of Sin apart from Christ, Sin told us what to do, and we obeyed, but now we have a new Master. And the difference is that we can trust this Master to do what is right and ask us to do what is right as well. So we consciously choose to submitted ourselves to God, so that he gives the orders and we follow them. This is actually a great freedom — the highest and deepest freedom to which we might be called, and available only to us as we choose to be slaves.