A.T. Robertson Commentary 1 Corinthians 14:27

"If any man speaketh in a tongue, [let it be] by two, or at the most three, and [that] in turn; and let one interpret:" — 1 Corinthians 14:27 (ASV)

By two (κατα δυο). According to two, ratio.

Or at most (η το πλειστον). Adverbial accusative, "or at the most."

Three (τρεις). Κατα to be repeated.

And that in turn (κα ανα μερος). One at a time and not over three in all.