en_tn_condensed/act/02/08.md

Why is it that we are hearing them, each in our own language in which we were born?

Possible meanings are 1) this is a rhetorical question that expresses how amazed they were or 2) this is a real question for which the people wanted an answer. (See: rc://en/ta/man/translate/figs-rquestion)

in our own language in which we were born

"in our own languages that we have learned from birth"

Parthians ... Arabians

This lists some of the many nations, regions, and cities from which they came. (See: rc://en/ta/man/translate/translate-names)

proselytes

"converts to the Jewish religion"