1 The burden of Damascus. Behold, Damascus is taken away from being a city, and it shall be a ruinous heap.
Damascus was the capital city of Syria.
2 The cities of Aroer are forsaken: they shall be for flocks, which shall lie down, and none shall make them afraid.
Aroer will become a place for sheep to safely rest. Only an empty city could be that, not a full busy one.
3 The fortress also shall cease from Ephraim, and the kingdom from Damascus, and the remnant of Syria: they shall be as the glory of the children of Israel, saith the LORD of hosts.
God is linking Syria and Israel here. Ephraim was the leading tribe of Israel. These two countries were partners.
4 And in that day it shall come to pass, that the glory of Jacob shall be made thin, and the fatness of his flesh shall wax lean.
They will no longer be rich enough to have enough food.
5 And it shall be as when the harvestman gather the corn, and reap the ears with his arm; and it shall be as he that gathers ears in the valley of Rephaim.
6 Yet gleaning grapes shall be left in it, as the shaking of an olive tree, two or three berries in the top of the uppermost bough, four or five in the outmost fruitful branches thereof, saith the LORD God of Israel.
God won’t kill them all, but leave a few here and there.
7 At that day shall a man look to his Maker, and his eyes shall have respect to the Holy One of Israel.
This will bring both countries back to worshiping God.
8 And he shall not look to the altars, the work of his hands, neither shall respect that which his fingers have made, either the groves, or the images.
No more idol worship.
9 In that day shall his strong cities be as a forsaken bough, and an uppermost branch, which they left because of the children of Israel: and there shall be desolation.
Their forts won’t save them. The countries will be destroyed.
10 Because thou hast forgotten the God of thy salvation, and hast not been mindful of the rock of thy strength, therefore shalt thou plant pleasant plants, and shalt set it with strange slips:
Both Syria and Israel had a history of serving God. But both had gone whole-hog into idolatry.
11 In the day shalt thou make thy plant to grow, and in the morning shalt thou make thy seed to flourish: but the harvest shall be a heap in the day of grief and of desperate sorrow.
No matter what they plant or how hard they work, when the enemy comes, they will be destroyed. They won’t get their crops.
12 Woe to the multitude of many people, which make a noise like the noise of the seas; and to the rushing of nations, that make a rushing like the rushing of mighty waters!
“You can yell and boast all you want. It won’t help you a bit.”
13 The nations shall rush like the rushing of many waters: but God shall rebuke them, and they shall flee far off, and shall be chased as the chaff of the mountains before the wind, and like a rolling thing before the whirlwind.
14 And behold at evening tide trouble; and before the morning he is not. This is the portion of them that spoil us, and the lot of them that rob us.
Both Israel and Syria had a history of persecuting true believers in God as well as waging war with Judah, who more often followed God's commands.