1 John 2:3

And hereby we do know that we know him, if we keep his commandments.
— 1 John 2:3, King James Version

In other translations

World English Bible (WEB)

This is how we know that we know him: if we keep his commandments.

American Standard Version (ASV)

And hereby we know that we know him, if we keep his commandments.

Young's Literal Translation (YLT)

and in this we know that we have known him, if his commands we may keep;