Thy prophets have seen vain and foolish things for thee: and they have not discovered thine iniquity, to turn away thy captivity; but have seen for thee false burdens and causes of banishment.
Thy prophets have seen vain and foolish things for thee. "Thy prophets," not God's (Jeremiah 23:26, "They are prophets of the deceit of their own heart").
Vain ... for thee - to gratify thy appetite, not for truth, but for deception. They have not discovered thine iniquity - in opposition to God's command to the true prophets (Isaiah 58:1). Literally, They have not taken off the vail which was on thine iniquity, so as to set it before thee.
Have seen for thee false burdens. Their prophecies were soothing and flattering; but the result of them, inasmuch as being "false," was heavy, burden-like calamities to the people, worse than even what the prophecies of Jeremiah, which they in derision called "burdens," threatened. Hence, he terms their pretended prophecies "false burdens," which proved to the Jews 'causes for their banishment' (Calvin).
[Samech (c)]