The Israelites were longing for the Day of the Lord, thinking that it would be a day of blessing for them. Amos, however, says it won’t be what you think it will be, and you won’t be on the side of it that you think you will be.
In Amos 5:10-13, we see a corrupt society where the wealthy elite maintain their wealth and power by dishonestly fixing the system in their favor. A just judge is despised. God’s punishment is appropriate: whatever you use your wealth to build will be taken from you before you can enjoy it.