John Gill Commentary Amos 3:10

"For they know not to do right, saith Jehovah, who store up violence and robbery in their palaces." — Amos 3:10 (ASV)

For they know not to do right, says the Lord
What is just and right between man and man, no, not in one single instance; they did not regard it, or advert to it; they were under no concern about it; and were so much under the power of their lusts, that they knew not how to do it; and had used themselves so long to such wicked and unjust ways, that they had lost at least the practical knowledge of doing justice; they knew what was right in the theory, but not in the practice; bribes blinded their eyes; for this seems to design judges, civil magistrates, such who had the administration of justice and the execution Of the laws in their hands.

The Targum is, ``they know not to execute the law;'' see (Jeremiah 4:22) ;

who store up violence and robbery in their palaces ;
treasured up riches in their palaces, gotten in a violent way, by oppression and injustice; and which was no other, nor better, than robbery. This shows that persons in power and authority, that lived in palaces, in great splendour and grandeur, are here meant.