Definition:
Prophetic warning refers to the messages delivered by prophets in the Bible, which serve as divine alerts or admonitions concerning future events, often calling for repentance and a return to righteousness. These warnings are typically directed towards individuals, nations, or groups who have strayed from God's commandments and are at risk of facing divine judgment.

Biblical Context:
Prophetic warnings are a central theme throughout the Bible, serving as a means by which God communicates His will and intentions to His people. These warnings are often accompanied by calls to repentance and are intended to guide the recipients back to a path of obedience and faithfulness.

Old Testament Examples:

1. Noah and the Flood:
In Genesis 6, God warns Noah of the impending flood due to the wickedness of humanity. Noah is instructed to build an ark to preserve his family and the animal species. This warning serves as a call to righteousness amidst widespread corruption.

2. Jonah and Nineveh:
The Book of Jonah recounts how God sends Jonah to the city of Nineveh to deliver a warning of impending destruction due to their wickedness. Jonah 3:4 states, "On the first day of his journey, Jonah set out into the city and proclaimed, 'Forty more days and Nineveh will be overturned!'" The people of Nineveh heed the warning, repent, and are spared from judgment.

3. Jeremiah's Warnings to Judah:
The prophet Jeremiah is tasked with delivering numerous warnings to the kingdom of Judah regarding their idolatry and disobedience. Jeremiah 25:4-5 says, "And the LORD has sent all His servants the prophets to you again and again, but you have not listened or inclined your ear to hear. The prophets told you, 'Turn now, each of you, from your evil ways and deeds, and you can dwell in the land the LORD has given to you and your fathers forever and ever.'"

New Testament Examples:

1. John the Baptist:
John the Baptist serves as a prophetic voice warning of the coming Messiah and the need for repentance. In Matthew 3:2 , he declares, "Repent, for the kingdom of heaven is near."

2. Jesus' Warnings:
Jesus Himself issues several prophetic warnings throughout His ministry. In Matthew 24, He warns of the destruction of the temple and the signs of the end times. Matthew 24:42 states, "Therefore keep watch, because you do not know the day on which your Lord will come."

3. The Book of Revelation:
The Apostle John receives visions that include warnings to the seven churches in Asia Minor. Revelation 2:5 warns the church in Ephesus, "Therefore, keep in mind how far you have fallen. Repent and perform the deeds you did at first. If you do not repent, I will come to you and remove your lampstand from its place."

Purpose and Significance:
Prophetic warnings serve multiple purposes in the biblical narrative. They are a demonstration of God's justice and mercy, offering a chance for repentance and redemption. These warnings also affirm God's sovereignty and His active role in guiding human history. They remind believers of the importance of obedience, faithfulness, and the consequences of turning away from God's commandments.

Theological Implications:
From a theological perspective, prophetic warnings underscore the holiness and righteousness of God. They highlight the seriousness of sin and the necessity of repentance. These warnings also emphasize the hope of restoration and the promise of salvation for those who heed God's call. Prophetic warnings are a testament to God's desire for His people to live in accordance with His will, reflecting His character and purposes in the world.