"Surely the Sovereign Lord does nothing without revealing his plan to his servants the prophets. The lion has roared - who will not fear? The Sovereign Lord has spoken - who can but prophesy?" NIV translation
Amos reminds the people that they had been warned about what God was going to do. At this point, they could choose to listen or act foolishly and disregard the signs.
In the same way, we have been warned through the prophecy given to John in the Book of Revelation. We can choose to ignore the signs of the times as Israel did, or we can choose to believe the Word of God but, regardless of whether we believe it or not, judgment is coming.
"Proclaim to the fortresses of Ashdod and to the fortresses of Egypt: 'Assemble yourselves on the mountains of Samaria; see the great unrest within her and the oppression among her people. They do not know how to do right,' declares the Lord, 'who hoard plunder and loot in their fortresses.'" NIV translation
God calls for the Philistines and the Egyptians to come forward and witness the condition of the kingdom of Israel. They had turned their back on the ways of God and so could not "know how to do right" as every kind of idolatry had become acceptable.
This is the ultimate cause & effect as we see that, when a nation turns its back on God and His ways, every idea of man becomes acceptable in their eyes. This leads to everyone being out for all they can get and ultimately the oppression of the poor. (Does this sound like our world today?)
"Therefore this is what the Sovereign Lord says: 'An enemy will overrun the land; he will pull down your strongholds and plunder your fortresses.'" NIV translation
God will punish sin and He will often use the ungodly as an instrument to do it. This verse was fulfilled when the Assyrians took Israel captive.
"This is what the Lord says: 'As a shepherd saves from the lion's mouth only two leg bones or a piece of an ear, so will the Israelites be saved, those who sit in Samaria on the edge of their beds and in Damascus on their couches.'" NIV translation
Just as the shepherd can save a part of the sheep from the lion, God is going to preserve a remnant of His people from this coming destruction. So, who will it be? We see that God saves those who are prepared (on the edge of their beds). So, how are they prepared? By faith, they believe the words that the prophet is sharing with them. This is a picture of salvation through Jesus Christ as all hear of Him and His sacrifice for all but only those who believe will be spared.
"'Hear this and testify against the house of Jacob,' declares the Lord, the Lord God Almighty. 'On the day I punish Israel for her sins, I will destroy the altars of Bethel; the horns of the altar will be cut off and fall to the ground. I will tear down the winter house along with the summer house; the houses adorned with ivory will be destroyed and the mansions will be demolished,' declares the Lord." NIV translation
God's judgment is total in that even the altar that they used was cast down and destroyed along with their fancy houses.
We have to ask ourselves whether we have let idolatry creep into our lives or not. Today, many live for material things such as their ever bigger homes, their bank accounts, or even their children and so we see the effects of this in the world today. A world where the love of most has grown cold.