Amos 3

Surely the Lord God does nothing,
Unless He reveals His secret to His servants the prophets. v.7

Read chapter 3
My old roommate hates surprises.  She thinks it's the worse thing to throw someone a surprise party.  When she was little she made her best friend tell her about the surprise party her parents were throwing her and she got mad at them for doing so.  I'm the opposite of her in that I would love a surprise birthday party.  But apart from surprise parties I do like to know what's going on as surprise happenings can cause stress easily.  We may not know when something is exactly going to happen but we can at least prepare for knowing it's coming soon.  Like when the weatherman says we're about to have the worst snow storm in twenty years this coming weekend, you start preparing beforehand.  Well the same goes with God.  He has revealed everything He's going to do to His mediators, who in turn reveal God's counsel to whom it is sent.  If He hasn't told them, he isn't going to do it, at least not until He tells them.
So in verses three through six God has just finished confirming with Israel that He is God omnipotent, He is the sovereign and Only God.  This leads to confirming that He is not going to do anything unless He reveals His secret counsel to mediators.  There are many things hidden that have now been made known.  Here the secret is what God's about to do to the tribes of Israel that Amos is going to tell them before all it takes place.
Do you know what God has said?  He's not a God that plays tricks on us or surprise attacks us.  Don't be ignorant of His words that you may prepare for what's to come laying up treasures in heaven.