Albert Barnes on Acts 5:21

Early in the morning. Greek, At the break of day. Comp. Lk 24:1, Jn 8:2.

Called the council together. The sanhedrim, 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 sanhedrim, but were men of age and experience, who (in Acts 4:8, 25:15) are called elders of the Jews, and who were present for the sake of counsel and advice in a case of emergency.

(g) "the high priest" Acts 4:5,6