So when Peter went up to Jerusalem, those of the circumcision took issue with him,

But when the Jews saw the large crowds [gathered to hear the Gospel] they became very jealous and took sharp issue with the things Paul said, and [even] spoke against them.

And [after] there was no little strife and debate by Paul and Barnabas against them, they appointed Paul and Barnabas and some others from among them to go up to the apostles and elders in Jerusalem concerning this issue.

Among others, some Epicurean and Stoic Philosophers joined issue with him. Some would ask "What is this prater wanting to make out?", while others would say "He seems to be a Preacher of foreign Deities." (This was because he was telling the Good News about Jesus and the Resurrection).

But if it is an issue about a word and names and the law from you, look ye yourselves, for I do not intend to be a judge of these things.

Since through you we enjoy great quietness, and since whatever has been undertaken for this nation has been conducted to a successful issue by your foresight at all times and in all places, we accept it, most excellent Felix, with all thankfulness.

The questions at issue referred to their own religion and to a certain Jesus who had died. Paul said he was alive.