Do not be childish
In your thinking!
But be mature
Ἀδελφοί, μὴ παιδία γίνεσθε ταῖς φρεσίν, ἀλλὰ τῇ κακίᾳ νηπιάζετε, ταῖς δὲ φρεσὶν τέλειοι γίνεσθε.
Paul told his Corinthian Christian brothers (Ἀδελφοί) that they should not be childish (μὴ παιδία γίνεσθε) in their thinking (ταῖς φρεσίν). But they should be babies or infantile (νηπιάζετε,) when it comes to evil (ἀλλὰ τῇ κακίᾳ). As far as thinking was concerned (ταῖς δὲ φρεσὶν), they should be mature in that regard (τέλειοι γίνεσθε). Only this Corinthian letter used this word φρεσὶν, that means heart, mind, thought, intellect, or understanding, and the word νηπιάζετε, that means to be an infant, childlike, childish, or infantile. Paul pointed out that the Corinthian preoccupation with tongue speaking was a sign of their immaturity. They should not be childish but mature in their thinking with an adult judgment. However, they should be childish like a young child in their moral innocence or lack of knowledge about evil. Paul would rather have the Corinthians mature in their good judgment and infantile in their moral ignorance of evil. Do you have a good mature thinking judgment?