What does Acts 23:4 mean?

Everywhere Paul goes, he starts at the synagogue and explains how Jesus of Nazareth fulfills the prophecies in the Jewish Scriptures. After a few weeks, invariably several Gentiles and a few Jews will believe him, but the leadership won't. Sometimes the leadership beats him (Acts 14:19), but usually they drive him out of the synagogue, and he and the new believers start a new church (Acts 18:4–7).

Here in Jerusalem, Paul has an opportunity to present Jesus to the Sanhedrin, the religious leaders of Judaism, but he doesn't get past his initial opening remark before his audience orders him struck (Acts 23:1–3).

Years before, Paul and the Sanhedrin enjoyed a more comfortable relationship. Paul had been trained by the famous Pharisee rabbi Gamaliel, one of the most respected members of the Sanhedrin (Acts 5:34; 22:3). Paul voluntarily became the Sanhedrin's enforcer, arresting Jesus-following Jews first in Jerusalem, Judea, and Samaria, and then farther north into Syria (Acts 8:1–3; 9:1–2).

During one such trip, however, Jesus appeared to Paul (Acts 9:3–5). Paul now understands that Jesus is the Jewish Messiah and the Son of God, and that worshiping Him is the fulfillment of Judaism. Because of this, he can claim a clear conscience before God (Acts 23:1). The council, however, considers this heresy.

The high priest Ananias has Paul struck (Acts 23:2). Paul responds by calling him a "whitewashed wall:" appearing respectable but filled with mold on the inside (Acts 23:3).

When Paul learns whom he has insulted, he says he didn't know (Acts 23:5). Ananias is known to history as a violent, greedy ruler not above using assassination to get what he wants. His order to strike Paul is illegal as Paul isn't even on trial, let alone convicted of a crime (Deuteronomy 25:1–3). Some say Paul didn't know Ananias gave the order because his eyesight had gone bad; others think he did know but is sarcastically saying he didn't think a high priest would act against the law.