Were the priests, the captain of the temple, and the Sadducees in Acts 4 Jews or Gentiles?
The priests, the captain of the temple, and the Sadducees mentioned in Acts 4 were all Jews. The context states there are no Gentiles involved among the temple priests, Sadducees, or Pharisees. They were part of the Jewish nation that opposed Peter's preaching about Jesus and the resurrection.
Les explains that in Acts 4, as they speak unto the people, the opposition comes from the Jewish nation—specifically the priests, the captain of the temple, and the Sadducees. He emphasizes that all these groups were Jews, with no Gentiles involved in the temple priesthood or among the Sadducees and Pharisees. The Sadducees were especially grieved because they denied any resurrection, believing one lived and died like an animal, so Peter's preaching that Christ was alive and could still come as King directly contradicted their doctrine. They challenged Peter for teaching something contrary to their belief.