New Living Translation
Dear brothers and sisters, don’t be childish in your understanding of these things. Be innocent as babies when it comes to evil, but be mature in understanding matters of this kind.

American Standard Version
Brethren, be not children in mind: yet in malice be ye babes, but in mind be men.

Berean Study Bible
Brothers, stop thinking like children. In regard to evil be infants, but in your thinking be mature.

Douay-Rheims Bible
Brethren, do not become children in sense: but in malice be children, and in sense be perfect.

English Revised Version
Brethren, be not children in mind: howbeit in malice be ye babes, but in mind be men.

King James Bible
Brethren, be not children in understanding: howbeit in malice be ye children, but in understanding be men.

World English Bible
Brothers, don't be children in thoughts, yet in malice be babies, but in thoughts be mature.

Young's Literal Translation
Brethren, become not children in the understanding, but in the evil be ye babes, and in the understanding become ye perfect;

1 Corinthians 14:20 Additional Translations ...