It will be a dark day. It will not be a day of deliverance for them but a day of judgment, judgment that they cannot escape now. And Amos uses images to show how, if a man is going to face judgment, he cannot escape it. Or if he escapes that he gets home only to lean his hand against the wall to rest and a snake bites him which was sunning on the roof. In other words, resistance is futile.
Judgment is inescapable.
I Hate Your Worship. More great reversals here. Anyone and everyone thought God would have enjoyed all the rituals, rites, sacrifices, and their enormous religiosity. They would have expected to hear from God's prophet how good they were and how much God was pleased with all this. But they hear the very opposite.