Through Paul’s captivity, the whole imperial guard has heard about Christ. The term imperial guard
does not necessarily refer to Rome. In every province, the Roman emperor had a representative, also with a bodyguard. Translations such as the whole court,
and the Roman headquarters
are also possible. Perhaps we should here think of the imperial guard in Caesarea.
The bottom line is that it has become clear to the entire court and everyone else why Paul is imprisoned. All the rest
refers to the people involved in the court, perhaps the citizens of the city as well.
In any case, many have heard about the prisoner Paul. It has become apparent to them that he was not arrested for some crime, but because he was proclaiming a new message. Naturally, this was widely discussed: what message does this man bring? Through those conversations people heard about Christ. Paul’s captivity is for Christ. This can be translated as: in Christ (literally translated) or for Christ.
13 so that it has become known throughout the whole imperial guard and to all the rest that my imprisonment is for Christ.