that our old man was crucified with [him], that the body of the sin may be made powerless, for our no longer serving the sin;
7 for he who hath died hath been set free from the sin.
we who died to the sin -- how shall we still live in it?4 for sin over you shall not have mastery.
3 are ye ignorant that we, as many as were baptized to Christ Jesus, to his death were baptized?
4 we were buried together, then, with him through the baptism to the death,
17 and thanks to God, that ye were servants of the sin, and -- were obedient from the heart to the form of teaching to which ye were delivered up;
18 and having been freed from the sin, ye became servants to the righteousness.
The writer of Romans 6 (likely Paul), is here using the fact that a literal slave was "freed" by means of death, to argue that since a Christian baptism was (in part) a death and burial, they were freed from the mastery of Sin.
This is clear by the expression that as Christians they were already 'set free from Sin' at their baptism.
As was discussed on another thread, this passage is being misunderstood by the WT. This led to the similarly erroneous conclusion that the resurrected dead are not judged by what they did in their previous life.