Acts gives us some interesting windows into the Judaism of the day. Take Gamaliel, for example. He was one of the most famous Pharisees at the time, and Acts says that Paul studied at his feet (Acts 22:3). There were two general schools of Pharisees: the School of Hillel and the School of Shammai. According to one tradition, Gamaliel was the grandson of the famous Hillel.
Hillel had a more fatalistic philosophy, similar to what we hear Gamaliel saying in Acts 5. If it is God’s will, God will do it. If it is not God’s will, we cannot fight against it. Shammai was more interested in helping God out. If it is to be, it is up to me. Ironically, Paul behaved more like someone from the School of Shammai than the School of Hillel.
Whatever teachers Paul had, he had actively tried to force God’s will by arresting Christians. He probably targeted Greek-speaking believers. He had several arrested and brought back to Jerusalem (22:4). Paul was present at Stephen’s stoning, but we should be careful about thinking Paul had a lot of Christians killed. The Romans put people to death, and Paul never tells us in his own writings that he brought about the deaths of early Christians. Paul was a “go-fer” for the Sanhedrin. He was not empowered to put people to death.
Because Paul says he cast his vote for the death of Christians (25:10), some have suggested that Paul himself might have been on the Sanhedrin. If he was, he would presumably have been married. As you might expect, this line of thought has led to further speculation. Did his wife die? Did she leave him when he became a Christian? Are there any hints in 1 Corinthians 7? Was he actually more Jesus’ age than a younger man?
Since Paul was sent out to arrest people, it is probably safer to think of him as someone who worked for the Sanhedrin rather than someone who was on the Sanhedrin. The vote he cast was thus a metaphorical one. When the Sanhedrin voted against early Christians, Paul was right there with them, on their side, “casting his vote” too. Again, we do not actually have a lot of evidence that the Sanhedrin put many Christians to death. For example, when the high priest Ananus had James stoned, he waited until there was no Roman governor in town.
Acts 23 also gives us an interesting window on the Sadducees, with whom Jesus also had a brief encounter in Luke 20:27-38. They tended to be aristocratic, priestly families. Many, although perhaps not all high priests came from this class (cf. Acts 5:17)... [for the rest, see this post]
P.S. Here's how a line from that post filled out: "It might be worthwhile to stop here and notice how easy it is to read our own situation into the Bible. So many think of the Sadducees as liberals because the liberals of our day do not believe in the supernatural.
"But this is completely wrong. The Sadducees strongly believed in the supernatural. In fact, their position on the afterlife was more “conservative” in relation to the Old Testament than the Pharisees’ position, which drew heavily on developments in Jewish belief in the time between the two testaments. The Sadducees were also more conservative in that they may have focused more on the Law and less on the other writings of the Old Testament."