Brothers and sisters, do not be children in your thinking; rather, be infants in evil, but in thinking be adults. In the law it is written, ‘By people of strange tongues and by the lips of foreigners I will speak to this people; yet even then they will not listen to me,’ says the Lord. Tongues, then, are a sign not for believers but for unbelievers, while prophecy is not for unbelievers but for believers. (1Corinthians 14: 20-22)

Paul is quoting Isaiah. The full context of the quote relates to the fall of Ephraim, the core of the Northern Kingdom of Israel, what was known in the time of Jesus as Samaria.

In Isaiah the Ephraimites are described as much blessed, but self-indulgent. "They are confused by wine, they stagger from strong drink; They reel while having visions." (Isaiah 28: 7) The prophet insists that they are too immature to learn knowledge.

Paul encourages what the translator has rendered as "in thinking be adults." The Greek is phren teleios. Phren is an intuitive understanding that combines both thinking and feeling. Teleios is purposeful, focused on outcomes, wholistic.

Perhaps better suited to our contemporary understanding would be: Brothers and sisters, do not be child-like in the way you engage and explain the world; be children in evil, but engage and explain the world maturely, mindfully, and purposefully.

Speaking in tongues is child-like. The practice is inclined toward immediate gratification. Paul encourages attention to less self-indulgent, more profound gifts of the spirit.

Above is a 17th Century icon from the Dionysiou Monastery representing Christ with the Samaritan Woman.