Amos asked seven rhetorical questions in verses 3-6 to help the Israelites appreciate the inevitability of their judgment. In each one the prophet pointed out that a certain cause inevitably produces a certain effect. The five questions in verses 3-5 expect a negative answer, and the two in verse 6 expect a positive one. Verses 7-8 draw the conclusion.
3:3-6 Two people do not travel together unless they first agree to do so. By implication, God and Israel could not travel together toward God's intended destination for the nation unless the Israelites agreed to do so on His terms (cf. v. 2).
3:4 A lion does not roar in the forest unless it has found prey. Young lions do not growl in their dens unless they have captured something and are protecting it (cf. 1:2).
3:5 Birds do not get snared in traps unless there is bait in the traps that attracts them. Animal traps do not snap shut unless something triggers them.
3:6 People do not tremble at the news of some coming danger unless someone blows a trumpet to warn them. Calamities do not occur in cities unless God has either initiated or permitted them.
"The seven examples of related events began innocuously, but become increasingly foreboding. The first example (Amos 3:3) had no element of force or disaster about it. The next two (v. 4), however, concerned the overpowering of one animal by another, and the two after that (v. 5) pictured man as the vanquisher of animal prey. In the final two examples (v. 6), people themselves were overwhelmed, first by other human instruments, then by God Himself. This ominous progression, to the point where God Himself is seen as the initiator of human calamity, brought Amos to a climactic statement (vv. 7-8)."37
3:7 A similar inevitable connection exists between two other events. God does nothing to His people unless He first warns them through one of His prophets (cf. Ps. 25:14; Jer. 23:18, 22).38
3:8 Amos drew the final comparison with allusion to his previous illustrations. The message of judgment coming from the Lord that Amos now brought the Israelites was like the roaring of a lion. Who would not fear such a lion as the sovereign Yahweh? Indeed, how could the mouthpiece of the lion not prophesy since Yahweh had spoken?