Acts 1:19 And it was known unto all the dwellers at Jerusalem; insomuch as that field is called in their proper tongue, Aceldama, that is to say, The field of blood.
Proponents of “Luke the Gentile” put forward this text to prove that Luke was a Gentile. In other words, Luke writes about Jews and speaks of “their proper tongue” – therefore he must not be a Jew, but rather a Gentile.
First, is Luke explaining or Peter speaking? If Peter is speaking, the question is settled. We know this does not prove Peter was not a Jew. However, if this is a parenthetical explanation by Luke, the question remains open.
Second, by tongue (διαλεκτω) here does Luke mean the bigger language of all the Jews (Hebrews) or a dialect of the inhabitants of Jerusalem? For example, Luke uses “the Hebrew tongue” to describe Paul speaking in Acts 21:40.
Third, by “their tongue” does he mean that of the dwellers at Jerusalem, thereby only distinguishing himself as not from Jerusalem (as opposed to him meaning he was not a Jew)? The language spoken by the Jews in Jerusalem was Aramaic. It is plain that the Galilean dialect used by Peter and the other apostles was different from the Jerusalem dialect (Matthew 26:73; Mark 14:70, Luke 22:59, Acts 2:7).
Even if Luke means the Hebrew language, it is simple to understand “their” distinguishing between Jews and the recipient of the letter (Theophilus) rather than Jews and the author of the letter (Luke). This verse does not lend strong support to the idea of Luke being a Gentile rather than a Jew.