A.T. Robertson Commentary Acts 21:34

"And some shouted one thing, some another, among the crowd: and when he could not know the certainty for the uproar, he commanded him to be brought into the castle." — Acts 21:34 (ASV)

Some shouting one thing, some another (αλλο αλλο τ επεφωνουν). Same idiom of αλλο αλλο as in 19:32 which see. The imperfect of επιφωνεω, to call out to, suits well the idiom. This old verb occurs in the N.T. only in Luke and Acts .

When he could not know (μη δυναμενου αυτου γνωνα). Genitive absolute of present middle participle of δυναμα with negative μη and second aorist active infinitive of γινωσκω.

The certainty (το ασφαλες). Neuter articular adjective from α privative and σφαλλω, to make totter or fall. Old word, in the N.T. only in Ac 21:34; 22:30; 25:26; Php 3:1; Hebrews 6:19.

Into the castle (εις την παρεμβολην). Koine word from παρεμβαλλω, to cast in by the side of, to assign soldiers a place, to encamp . So παρεμβολη comes to mean an interpolation, then an army drawn up (Hebrews 11:34), but mainly an encampment (Hebrews 13:11,13), frequent in Polybius and LXX. So here barracks of the Roman soldiers in the tower of Antonia as in verse 37; 22:24; 23:10,16,32.