5:18 The prophet began his message by crying, "Alas"(Heb., hoy, woe, oh). This word announced coming doom, another funeral lament (cf. v. 1). Many Israelites in Amos' day were looking forward to a coming day of the Lord. Former prophets had spoken of a day in which Yahweh would conquer His enemies and the enemies of His people and establish His sovereign rule over the world (e.g., Joel 3:18-21, and perhaps Isa. 24:21-23; 34:1-3, 8). The Israelites knew that this was going to be a time of great divine blessing, but Amos informed them that it would also be a time of divine chastisement. It would be a time of darkness rather than light (cf.; Jer. 46:10; Joel 3:1-17; Zeph. 3:8; Zech. 14:1-3). God would judge His people before He blessed them.
5:19 The coming day of the Lord would mean inescapable tragedy for Israel. The Israelites may have thought they had escaped one enemy, but they would have to face another. They might think they were secure and safe in their homeland, but deadly judgment would overtake them in that secure environment. There would be no safe haven from God's coming judgment.
5:20 Rhetorically Amos stated that the coming day of the Lord would be a day characterized by darkness and gloom (despair) rather than by bright light (joy; cf. Joel 2:1-2, 10-11; Zeph. 1:14-15).
A brighter day of the Lord was also coming (cf. 9:11-15; Jer. 30:8-11; Hos. 2:16-23; Mic. 4:6-7; Zeph. 3:11-20), but first a dark one would appear. The Israelites wanted to hasten the good day of the Lord, but they wanted to forget about the bad one. This prophecy found fulfillment when the Assyrians overran Israel and took most of the people into exile in 722 B.C. The later Tribulation period for Israel, which will precede her millennial day of blessing, will be similar to what Amos predicted here, but I think it was not what God was foretelling here.
