Charles Ellicott Commentary 1 Corinthians 14:28

"but if there be no interpreter, let him keep silence in the church; and let him speak to himself, and to God." — 1 Corinthians 14:28 (ASV)

But if there be no interpreter.—But if there is no one with the gift of interpreting, then the speaker with tongues was not to exercise his gift publicly at all; he may only exercise his gift in private with himself and God.