Expositor's Bible Commentary Commentary 1 Corinthians 14:5

"Now I would have you all speak with tongues, but rather that ye should prophesy: and greater is he that prophesieth than he that speaketh with tongues, except he interpret, that the church may receive edifying." — 1 Corinthians 14:5 (ASV)

Paul emphatically restates v.1b: Speak in tongues, you Corinthians, yes; but more than that, I want you to prophesy, because this gift brings understanding and strengthening to the church. However, if there is an interpretation of the tongue, then speaking in tongues can strengthen the church.