Albert Barnes Commentary Acts 5:21

"And when they heard [this], they entered into the temple about daybreak, and taught. But the high priest came, and they that were with him, and called the council together, and all the senate of the children of Israel, and sent to the prison-house to have them brought." — Acts 5:21 (ASV)

Early in the morning. Greek, At the break of day. Compare to Luke 24:1; John 8:2.

Called the council together. The Sanhedrin, or the great council of the nation. This was clearly for the purpose of trying the apostles for disregarding their commandments.

And all the senate. Greek, Eldership. Probably these were not a part of the Sanhedrin, but were men of age and experience, who (Acts 25:15) are called elders of the Jews, and who were present for the sake of counsel and advice in a case of emergency.