John C. Poirier, «The Narrative Role Of Semitic Languages In The Book Of Acts», Vol. 16 (2003) 107-116
Philological studies have suggested that “the Hebrew dialect” (th|= (Ebra1%di diale/ktw|) in Acts 21,40; 22,2; and 26,14 refers to Hebrew, not Aramaic. But why would Paul speak Hebrew when addressing fellow Jews? This article suggests that he did so in order to be understood by the Jews but not by the Roman tribune (who would have understood Aramaic). This scenario is supported by a number of details within the account, and by a parallel case in 4 Maccabees. The article also suggests that something similar lies behind the use of Hebrew by the resurrected Jesus (26,14).