What was Paul's Second Imprisonment?
The second imprisonment of the Apostle Paul occurred in 6-/68 AD and is mentioned in 2 Timothy 4. When Paul writes again to Timothy he has had a winter in prison, and has suffered greatly from the cold and does not wish to spend another winter in the Mamertine (probably) prison (2Ti 4:13,21). We do not know what the charges now are. They may have been connected with the burning of Rome. There were plenty of informers eager to win favor with Nero. Proof was not now necessary.
Christianity is no longer a religio licita under the shelter of Judaism. It is now a crime to be a Christian. It is dangerous to be seen with Paul now, and he feels the desertion keenly (2Ti 1:15 ff; 2Ti 4:10).
Only Luke, the beloved physician, is with Paul (2Ti 4:11), and such faithful ones as live in Rome still in hiding (2Ti 4:21). Paul hopes that Timothy may come and bring Mark also (2Ti 4:11). Apparently Timothy did come and was put into prison (Heb 13:23). Paul is not afraid. He knows that he will die.
He has escaped the mouth of the lion (2Ti 4:17), but he will die (2Ti 4:18). The Lord Jesus Christ stood by him, perhaps in visible presence (2Ti 4:17).
The tradition is, for now Paul fails us, that Paul, as a Roman citizen, was beheaded on the Ostian Road just outside of Rome. Nero died June, 68 AD, so that Paul was executed before that date, perhaps in the late spring of that year (or 67).
Perhaps Luke and Timothy were with him. It is fitting, as Findlay suggests, to let Paul's words in 2Ti 4:6-8 serve for his own epitaph. He was ready to go to be with Jesus, as he had long wished to be (Php 1:23).Source:
International Standard Bible Encyclopedia, which is in the public domain (with minor edits).