A.T. Robertson Commentary Acts 4:5

"And it came to pass on the morrow, that their rulers and elders and scribes were gathered together in Jerusalem;" — Acts 4:5 (ASV)

Rulers and elders and scribes (τους αρχοντας κα τους πρεσβυτερους κα τους γραμματεις). The three classes composing the Sanhedrin (rulers=chief priests who were Sadducees, the scribes usually Pharisees, the elders not in either class: 24 priests, 24 elders, 22 scribes).

Were gathered together (συναχθηνα). First aorist passive infinitive of συναγω with accusative of general reference and the subject of εγενετο.