But be ye doers of the word, and not hearers only, deceiving your own selves. For if any be a hearer of the word, and not a doer, he is like unto a man beholding his natural face in a glass: For he beholdeth himself, and goeth his way, and straightway forgetteth what manner of man he was. But whoso looketh into the perfect law of liberty, and continueth therein, he being not a forgetful hearer, but a doer of the work, this man shall be blessed in his deed.
[KJV (1611)]

But you must do what the word tells you, and not just listen to it and deceive yourselves. To listen to the word and not obey is like looking at your own features in a mirror and then, after a quick look, going off and immediately forgetting what you looked like. But the man who looks steadily at the perfect law of freedom and makes that his habit -- not listening and then forgetting, but actively putting it into practice -- will be happy in all that he does.
[JB (1966)]

But you must do what the Word tells you and not just listen to it and deceive yourselves. Anyone who listens to the Word and takes no action is like someone who looks at his own features in a mirror and, once he has seen what he looks like, goes off and immediately forgets it. But anyone who looks steadily at the perfect law of freedom and keeps to it -- not listening and forgetting, but putting it into practice -- will be blessed in every undertaking.
[NJB (1985)]

You must be doers of the word and not only hearers who mislead themselves. Those who hear but don’t do the word are like those who look at their faces in a mirror. They look at themselves, walk away, and immediately forget what they were like. But there are those who study the perfect law, the law of freedom, and continue to do it. They don’t listen and then forget, but they put it into practice in their lives. They will be blessed in whatever they do.
[CEB (2011)]

Do not merely listen to the word, and so deceive yourselves. Do what it says. Anyone who listens to the word but does not do what it says is like a man who looks at his face in a mirror and, after looking at himself, goes away and immediately forgets what he looks like. But the man who looks intently into the perfect law that gives freedom, and continues to do this, not forgetting what he has heard, but doing it -- he will be blessed in what he does.
[NIV (2011 ed.)]

But be doers of the word and not merely hearers who deceive themselves. For if any are hearers of the word and not doers, they are like those who look at themselves[a] in a mirror; for they look at themselves and, on going away, immediately forget what they were like. But those who look into the perfect law, the law of liberty, and persevere, being not hearers who forget but doers who act -- they will be blessed in their doing.
[NRSV (2021 ed.)]