The phrase in church
confirms that the setting Paul has in mind is the public worship service. The number five
as opposed to the number ten thousand
indicates how vastly superior intelligible speech is to unintelligible speech. The verb translated as instruct
is katecheo, which is often used for systematic teaching. It is from this word that we get the English word catechism.
19 Nevertheless, in church I would rather speak five words with my mind in order to instruct others, than ten thousand words in a tongue.