Adam Clarke on Ezra 4:14

Now because we have maintenance from the king's palace - More literally: Now because at all times we are salted with the salt of the palace; i.e., We live on the king's bounty, and must be faithful to our benefactor. Salt was used as the emblem of an incorruptible covenant; and those who ate bread and salt together were considered as having entered into a very solemn covenant. These hypocrites intimated that they felt their conscience bound by the league between them and the king; and therefore could not conscientiously see any thing going on that was likely to turn to the king's damage. They were probably also persons in the pay of the Persian king.