What does Acts 5:23 mean?

The chief priests have arrested the apostles for preaching in Jesus' name after they had ordered the apostles not to (Acts 4:17–18). The next morning, as the whole council waits to question them, officers go to the prison cells and find them empty. They don't know that earlier that night, God had sent an angel to free His messengers and return them to the temple courtyard to continue preaching (Acts 5:17–23).

A short time before, the priests made sure Jesus' body was even more secured than the apostles. They poured wax over the seam between the great stone and the rock face so that if anyone tried to move the stone the wax would crack. They posted guards around the tomb. But the guards didn't see men come to move the stone, they saw an angel, white as snow and as bright as lightening, roll back the stone and sit on it. The guards were so terrified they "became like dead men" (Matthew 27:4). Meanwhile, the angel spoke to the women at the tomb, telling them that Jesus had risen from the dead and to go and tell the disciples. The guard, on the other hand, went and reported the incident to the chief priests, who bribed them with money and protection to claim that the disciples had stolen Jesus' body (Matthew 27:62–28:15).

The guards standing outside the apostles' prison cells are spared the awesome horror of an earthquake and an angel, so they have no idea they are guarding empty rooms. They are very fortunate they arrested the apostles on behalf of the priests and not the Roman army. When Peter is arrested by Herod Agrippa I, and an angel comes to release him, Herod has the sentries executed (Acts 12:1–19). For now, the temple captain and the priests are just "perplexed" (Acts 5:24). Once again, instead of going to their Scriptures to see how current events relate to the prophets, they try to use their own wisdom to find the path forward.