What does Acts 4:9 mean?
Peter and John are defending themselves before the Sanhedrin. What, exactly, they're defending is a bit confusing. While going to the temple to pray, Peter healed a lame man (Acts 3:1–10). When the other worshipers crowded them, wanting to know where Peter received his ability to heal, Peter and John explained it was by the power of Jesus, who died and rose again (Acts 3:11–26). The priests and Sadducees, who did not believe in the resurrection of the dead, arrested them, "greatly annoyed because they were teaching the people and proclaiming in Jesus the resurrection from the dead" (Acts 4:2). But their question is, "By what power or by what name did you do this?" (Acts 4:7).Peter starts out almost innocently. Were they really arrested for this good deed? That a huge crowd saw? The same crowd that saw the temple guard take them away? Peter's comment hits its mark, and eventually the Sanhedrin will let them go: "When they had further threatened them, they let them go, finding no way to punish them, because of the people, for all were praising God for what had happened" (Acts 4:21). Still, Peter is more than willing to be witness to Jesus' resurrection to the Sanhedrin. And, eventually, some will listen (Acts 6:7).
Later, when the Sanhedrin arrests all the apostles, Luke will reveal the council's real problem with the Jesus-followers. Peter and John weren't preaching the destruction of the temple, like people claimed of Jesus (Mark 14:57–59) and Stephen (Acts 6:12–14). They weren't healing on the Sabbath, like the Pharisees often criticized Jesus for (Mark 3:1–4; Luke 13:10–17; 14:1–6). And it wasn't illegal to teach the resurrection; the Pharisees believed in the resurrection. Rather, the chief priests and Sadducees were jealous (Acts 5:17). Jerusalem was their town, and they didn't want to share. When someone believes this life is all they have, it's disturbing what they'll do to protect it.