Albert Barnes Commentary Jeremiah 23:33

"And when this people, or the prophet, or a priest, shall ask thee, saying, What is the burden of Jehovah? then shalt thou say unto them, What burden! I will cast you off, saith Jehovah." — Jeremiah 23:33 (ASV)

Burden – Here it means a prophecy, either:

1. As being something weighty; or
2. As something proclaimed aloud.

Isaiah brought the word into general use: Jeremiah never used it, though his predictions were all of impending evil. The false prophets, however, applied it in derision to Jeremiah’s prophecies, playing upon its double sense, and so turning solemn realities into mockery .

What burden? – Or, according to another reading, You are the burden.

I will even forsake you – Rather, and I will cast you away. From the idea of a burden, the thought naturally arises of refusing to bear it and throwing it off.