Paul uses the powerful image of slavery. If we're truly free in Christ, why does he keep talking about being 'slaves'?
Paul isn't saying Christians are literally slaves in a degrading way. Instead, he's using a familiar concept to illustrate a profound shift in allegiance. Before Christ, believers were slaves to sin, their 'members' (body parts, actions, faculties) used for impurity and lawlessness. Now, through Christ, they have been freed from that bondage.
However, this freedom doesn't mean anarchy. It means being transferred to a new Master. Just as before, their whole being was given over to sin, now their whole being is to be given over to righteousness. This isn't about forced labor, but a willing, joyful surrender to the One who redeemed them. It's a deliberate choice to present ourselves to God, allowing His righteousness to work through us, leading to our ongoing transformation (sanctification).