Some Greek manuscripts omit the words of sin, but the UBS Committee on the Greek text judges that these words are a part of the original text, though rating their decision a “C” choice. The phrase was perhaps omitted from some ancient manuscripts in an attempt by a scribe to make a stylistic improvement, since the omission would place the two mentions of a slave closer together. Moffatt, Phillips, and New English Bible omit of sin. Whether or not this phrase was an original part of the text, its meaning is implied. In some translations it may have to be necessary to say explicitly that the slavery to which Christ refers is slavery to sin.

It may be difficult in some languages to speak of “a slave of sin.” If so, such an expression as “just like a slave obeying sin” may be employed. However, to do so requires personification of “sin.” It is more likely that one can translate “a slave to his desire to sin” or “a slave controlled by his desires to sin.”

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on the Gospel of John. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .