Jeremiah ch. 23 is about false prophets.
Jer 23:1 Woe be unto the pastors that destroy and scatter the sheep of my pasture! saith the Lord.
The phrase “burden of the Lord” is as if the Lord has put a divinely ordered task (or burden) on the person to relay a message from the Lord. It is the same as saying “The Lord told me…” or “Thus saith the Lord…”
In Jer.23:32-40 the people, the prophets, or priests would go around using this phrase to lend “divine authority” to what they were saying.
Basically they would go around saying “The Lord told me … ” about anything and everything.
This debases, or lowers the value of God’s words and since it is assigning God’s authority to it, is a form of taking the Lord’s name in vain.
We should not attribute something as “the Lord told me” unless we are absolutely sure it is the Lord giving the utterance and it should never be despised or taken lightly (1 Thess 5:20).
If it is a message from the Lord, then it should not be confusing or contradictory to His written words.
Also, if it is a message from the Lord, it should be taken seriously, revered and obeyed — not treated lightly.
Jesus says:
Mt 5:37 But let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil
Jesus also tells us that we will give an account for every idle word…
Mt 12:36-37 But I say unto you, That every idle word that men shall speak, they shall give account thereof in the day of judgment. For by thy words thou shalt be justified, and by thy words thou shalt be condemned