12 Heb “Be on your guard … Do not trust.” The verbs are second masculine plural of direct address and there seems no way to translate literally and not give the mistaken impression that Jeremiah is being addressed. This is another example of the tendency in Hebrew style to turn from description to direct address (a figure of speech called apostrophe).
13 Heb “cheating, each of them will cheat.” There is perhaps an intentional pun and allusion here to Gen 27:36 and the wordplay on the name Jacob there. The text here reads עָקוֹב יַעְקֹב (’aqob ya’qob).
14 Heb “their tongues.” However, this is probably not a natural idiom in contemporary English and the tongue may stand as a part for the whole anyway.

In other versions

ESVEnglish Standard Version

Let everyone beware of his neighbor,

and put no trust in any brother,

for every brother is a deceiver,

and every neighbor goes about as a slanderer.

Everyone deceives his neighbor,

and no one speaks the truth;

they have taught their tongue to speak lies;

they weary themselves committing iniquity.

NIVNew International Version (2011)

“Beware of your friends;

do not trust anyone in your clan.

For every one of them is a deceiver,

and every friend a slanderer.

Friend deceives friend,

and no one speaks the truth.

They have taught their tongues to lie;

they weary themselves with sinning.

CSBChristian Standard Bible

Everyone has to be on guard against his friend.

Don’t trust any brother,

for every brother will certainly deceive,

and every friend spread slander.

Each one betrays his friend;

no one tells the truth.

They have taught their tongues to speak lies;

they wear themselves out doing wrong.

NLTNew Living Translation

“Beware of your neighbor!

Don’t even trust your brother!

For brother takes advantage of brother,

and friend slanders friend.

They all fool and defraud each other;

no one tells the truth.

With practiced tongues they tell lies;

they wear themselves out with all their sinning.

LEBThe Lexham English Bible

“Let everyone be on your guard against his neighbor,

and you must not trust in any brother,

for everyone surely betrays,

and every neighbor goes about with slander.

And everyone deceives his neighbor,

and they do not speak the truth,

they have taught their tongues to speak lies,

they are tired from going astray.

KJV 1900King James Version

Take ye heed every one of his neighbour,

And trust ye not in any brother:

For every brother will utterly supplant,

And every neighbour will walk with slanders.

And they will deceive every one his neighbour,

And will not speak the truth:

They have taught their tongue to speak lies,

And weary themselves to commit iniquity.

Public Domain