1 Corinthians 14:24

But if all prophesy, and there come in one unbelieving or unlearned, he is reproved by all, he is judged by all.

If all prophesy ... This answers to "if all speak with tongues" in the preceding verse; but what is meant in both cases is a reference to "all who participate publicly," instead of being an affirmation that all were speaking at one time. However, despite the absence of that thought from this particular verse, it was true of the tongue-speakers that they were all speaking at once. This is a mandatory conclusion based on Paul's order that the speakers should speak "one at a time," or "in turn" (1 Corinthians 14:27).

Reproved by all, ... judged by all ... has reference to the power of a decently ordered service featuring intelligible speakers to move the unregenerated to accept the gospel, as stated in the next verse.