The phrase "in that day" is a significant eschatological term found throughout the Bible, often used by the prophets to refer to a future time of divine intervention, judgment, or restoration. This expression is particularly prevalent in the prophetic books of the Old Testament and is also echoed in the New Testament, pointing to the fulfillment of God's promises and the culmination of His redemptive plan.

Old Testament Usage

1. Judgment and Restoration: The prophets frequently use "in that day" to describe both impending judgment and the hope of restoration. For instance, Isaiah speaks of a day when the Lord will punish the proud and exalt the humble: "The haughtiness of man will be humbled, and the pride of men brought low; the LORD alone will be exalted in that day" (Isaiah 2:17). This dual theme of judgment and restoration is a common motif, emphasizing God's justice and mercy.

2. Messianic Prophecies: "In that day" is also used in the context of messianic prophecies. Zechariah prophesies about a future king and the establishment of peace: "In that day the LORD will defend the inhabitants of Jerusalem, so that the weakest among them will be like David, and the house of David will be like God, like the Angel of the LORD going before them" (Zechariah 12:8). This points to the coming of the Messiah and the ultimate victory of God's people.

3. The Day of the Lord: The phrase is often synonymous with "the Day of the Lord," a time of divine reckoning. Joel describes it as a day of darkness and gloom, yet also a time of deliverance for those who call on the name of the Lord: "And it shall come to pass that everyone who calls on the name of the LORD will be saved; for on Mount Zion and in Jerusalem there will be deliverance, as the LORD has promised, among the remnant called by the LORD" (Joel 2:32).

New Testament Fulfillment

1. The Coming of Christ: In the New Testament, "in that day" often refers to the return of Christ and the final establishment of His kingdom. Jesus Himself uses the phrase to speak of His second coming and the gathering of His elect: "At that time they will see the Son of Man coming in a cloud with power and great glory" (Luke 21:27).

2. Judgment and Reward: The New Testament writers continue the theme of judgment and reward associated with "in that day." Paul, in his letters, speaks of a day when each person's work will be tested: "If what he has built survives, he will receive a reward. If it is burned up, he will suffer loss. He himself will be saved, but only as if through the flames" (1 Corinthians 3:14-15).

3. Eternal Hope: The phrase also encapsulates the hope of eternal life and the fulfillment of God's promises. In 2 Timothy, Paul expresses his confidence in the Lord's righteous judgment: "The Lord will rescue me from every evil deed and will bring me safely into His heavenly kingdom. To Him be the glory forever and ever. Amen" (2 Timothy 4:18).

Theological Significance

The recurring use of "in that day" throughout Scripture underscores the certainty of God's sovereign plan and the assurance of His ultimate victory over sin and death. It serves as a reminder of the hope and accountability that believers have in anticipation of the fulfillment of God's promises. This phrase encapsulates the tension between the "already" and the "not yet" of the Christian faith, pointing to the present reality of salvation and the future consummation of God's kingdom.