Romans 6:15-19

Throughout Romans, we learn about how we are under grace rather than law. But that doesn't mean that sinning is a good idea! One natural side effect of sin is that sin ruins lives.

But not only that, but focusing on sin can have an effect on behavior. Paul talked about how when we "present [ourselves] slaves to obey", we are "that one's slaves whom [we] obey" (6:16). I know that freedom is an important concept, but if we think about these verses a little bit more, Paul actually seems to have a point. The influence we have can affect our behavior, whether for better or for worse, and we see this pattern in life. For instance, when people choose to get drunk, they can have a tendency to get drunk again, which can lead to "addiction". That's why there are various calls to pay attention to our influences (both from Christians and non-Christians).

However, although the Roman Christians had been "slaves of sin", the Roman Christians still obeyed "that form of doctrine to which [they] were delivered" (6:17). Additionally, the Roman Christians became "slaves of righteousness" (6:18). Sometimes referred to as "servants of righteousness" in translations like KJV. Basically, the Roman Christians decided to put God and righteousness as their main influence.

It should be noted that the talks on slaves and servants is an analogy (not to mention that slavery in the Bible is more of indentured servitude rather than the racial abuses you may be familiar with). It's likely that some translations favor "slave" rather than "servant" due to the stronger effect. Paul even stated that he "speak[s] in human terms because of the weakness of [...] flesh" (6:19).

In the end, compared to the two masters, the master of righteousness is a lot better than the master of sin (or even self-master, which has a difficulty of direction and doesn't really end well). This master is also "for holiness" (6:19), which is basically being set apart.