The phrase Day of the Lord describes a time when God judges his enemies with righteous punishment. The ungodly receive the punishment they deserve, while the righteous gain their complete salvation (see Isaiah 3:16–4:6). On this day, God shows his powerful control over creation. When God appears in glory, people feel fear (2:10, 19, 21). This is because he examines all human support systems. This includes religious, economic, military, and social structures.
This phrase first appears in the prophecy of Amos (Amos 5:18). But it did not start with him. Amos corrected a common misunderstanding among the Israelites. They thought the day of the Lord would be a joyful day of salvation. They believed God would judge Israel's enemies and restore Israelite rule over greater Canaan.
Yet, Amos warned that the day of the Lord would bring darkness, not light. This was because the people were rebelling against God (see Amos 5:10–12, 21–27). The Israelites were confident that God was always on their side. But their sins made them God's enemies, deserving full punishment.
The prophets often used the phrase "that day" to describe an important event (see Isaiah 2:11; 27:1; Zephaniah 1:8). Because of God's warnings and the people's sins, the prophets saw "that day" as near (see Joel 1:15; 2:1). They hoped their warnings would cause God's people to repent (see Zephaniah 2:1–3). Unfortunately, most people ignored these warnings.
The day of the Lord arrived for the northern kingdom when Assyria destroyed Samaria. It came for the southern kingdom when Babylon invaded and destroyed Jerusalem between 605 and 586 BC.
The day of the Lord is disastrous for ungodly people. The prophet Joel compares its destruction to a locust plague (Joel 1:1–2:11). Yet, this day guarantees God's people that he is sovereign and just. It is a day of salvation for those who obey the prophets and "everyone who calls on the name of the LORD" (see Joel 2:31–32).
The same God who brings destruction to his enemies will be a refuge and stronghold for his people (Joel 3:16). Nations used by God to judge Israel and Judah will later experience their own "day of the Lord" (see, for example, Isaiah 13:4–22; Ezekiel 30:1–5; Obadiah 1:15–16).
The Old Testament prophets mostly regarded judgment as happening during the exile of the Israelites to Babylon. New Testament writers use the phrase Day of the Lord to describe Jesus' return as the judge of the world. That day "will come like a thief" (2 Peter 3:10; see also 1 Thessalonians 5:2–4). Therefore, God's people must be ready, or they will experience an end similar to those who ignored the prophets' warnings.
Passages for Further Study
Isaiah 2:10–22; 4:1–6; 13:4–12; Ezekiel 30:1–5; Joel 1:13–15; 2:1–11, 28–32; 3:9–16; Amos 5:18–24; Obadiah 1:15–16; Zephaniah 1:2–18; Malachi 4:1–5; 1 Corinthians 1:8; 5:5; 1 Thessalonians 5:2; 2 Thessalonians 2:2; 2 Timothy 1:18; 2 Peter 3:10; Revelation 20:1–15