In Amos 3:7, the prophet says “Yahweh God does nothing unless He reveals His secret counsel to His servants the prophets.” This is a fairly obvious allusion back to Genesis 18:17-18, where Yahweh says, “Shall I hide from Abraham what I am about to do, since Abraham will surely become a great and mighty nation, and in him all the nations of the earth will be blessed?” And Yahweh goes on to inform Abraham, the prophet (Gen 20:7) about the impending destruction of Sodom and Gomorrah.
Amos 3 begins with a reminder of the exodus, and a threat that Yahweh is going to “punish [Israel] for all your iniquities” (v 2). The animal symbols in vv 4-5 describe the threat to the Northern kingdom, and in verse 6 Amos explicitly refers to a trumpet announcing a calamity in a city. Verses 11 make it clear that Israel and Samaria are the targets of wrath: “An enemy, even one surrounding your land, will pull down your strength from you and your citadels will be looted” (v 11) and “just as the shepherd snatches from the lion’s mouth a couple of legs or a piece of an ear, so will the sons of Israel dwelling in Samaria be snatched away” (v 12). The predators will attack and kill, and only a few bits and pieces of the body that was Israel will be saved.
The allusion in Amos 3:7 brings the Sodom situation to bear on Amos’s day. Amos the prophet is like Abraham the prophet. And both have been informed by Yahweh that a city is going to be destroyed. Thus, Amos 3:7 is a subtle hint that Samaria has become a Sodom, and will be destroyed in a similar fashion, with only a handful of survivors. This hint of Amos, of course, is made explicit elsewhere in the propetic literature, where Jerusalem and Samaria are explicitly compared to Sodom and Gomorrah.