v1-2: Introduction; Amos the man, a shepherd, living in a rural community; and his background is reflected in some of his words. For example, in 2.13, a cart loaded with sheaves; in 6.12, Does one plough there with oxen?
Tekoa is South West of Bethlehem, and Amaziah tells Amos to return to his own land, 7.12.
The historical context is 2 Kings 14.23-29; Jeroboam was a powerful king, although he continued in the sins of his ancestors. The earthquake, see Zech 14.5, was a sign of God's judgment upon Israel.
The voice of the Lord from Zion, see Joel 3.16; the lion roaring; and there is much about God's judgment here. The phrase "this is what the Lord says," or similar, appears 54 times.
Amos opens, v3-2.3, with judgment upon the nations surrounding Israel (Joel 3.12), esp. for their attacks upon Israel.
v3-5: Damascus, and the people or Aram (Syria); they threshed Gilead with sledges of iron. Hazael is known for his cruelty, 2 Kings 8.12. They will suffer exile.
v6-8: Gaza, and the people of Philistia; they took captive the whole community, to sell them as slaves to Edom. They will suffer a thorough judgment, "till the last of the Philistines is dead."
v9-10: Tyre also sold whole communities to Edom. They were treacherous, laying aside a previous treaty, perhaps from 1 Kings 5.1. Tyre will suffer fire to consume her fortress, on which she depended.
We see that God is not capricious, nor random, in His works. Judgment falls for good reason. The following nations, Edom, Ammon, and Moab, are Semitic peoples, from Abraham's family.
v11-12: Edom pursued his brother with the sword, and acted without compassion and mercy; 2 Chr 11.4.
v13-15: Ammon practised cruelty in ripping open the women of Gilead, in extending her borders.