Why did Paul say he would rather speak five words with understanding than ten thousand words in an unknown tongue?
Paul prioritized understandable speech in the worship service because the purpose was to teach others. Although he could speak more languages than they did, he said five words with understanding that instruct the congregation were better than ten thousand words in an unknown tongue no one could understand.
Les explains that Paul had a special gift to communicate the Gospel in various languages and dialects as Christianity was just getting off the ground. Paul says he spoke with those languages more than they all did. Yet in the church, congregation, and worship service, the goal was not to display that gift but to speak with understanding so his voice might teach others also. Five understandable words that instruct others are better than ten thousand words in an unknown tongue. Les also notes Paul's call: be not children in understanding but grow up and be men.
Yet in the church I had rather speak five words with my understanding, that by my voice I might teach others also, than ten thousand words in an unknown tongue.