How can I reconcile the God of the Old Testament who destroys nations of people, with the Jesus of the New Testament who offers mercy and love?
Many Bible students have wrestled with what seems to be a contradiction between the God of the Old Testament and the God of the New Testament. In the Old Testament they read accounts of God directing Israel to utterly destroy its enemies, while in the New Testament Jesus and the Apostles tell us to forgive our enemies and show grace to those who persecute us. Are these two persepctives in conflict?
The answer is no, and to understand why, we need to seek a better understanding of God's true nature and the teaching of Scripture concerning this question. While we could fill books with a full discussion of this topic (and many authors have already), we will try to offer a brief overview now while encouraging you to study this question further on your own.
At the heart of this question is the consistency of God's character. When we ask if the OT and NT gods are different, we suggest that God's character is limited to either mercy or judgment but He cannot display both. This assumption is simply not reasonable nor biblically accurate.
Scripture teaches that God's character remains consistent throughout the Old Testament and New Testament. From Genesis to Revelation, God is shown to be a God of love, mercy and patience. Similarly, both the OT and NT reveal God's wrath, anger, and vengeance. Thumbing through the pages of both the OT and the NT you will find many references a loving Father Who extends mercy and grace even to His enemies, and you will also find a God who hates sin and is willing to demonstrate His wrath against sinners. Both sides of God are represented in both testements. Therefore, to think that the OT and NT depict different gods is an erroneous assumption in iteself.
Furthermore, it is illogical to assume that God cannot be loving and merciful while also demonstrating wrath against sin. Love, mercy, wrath and judgment are not mutually exclusive character traits. In fact, they are complimentary personality traits. It is no more contradictory to say that God can display both wrath and mercy than it is to say we can feel both love and hatred from time to time.
Thirdly, real personalities are multifaceted and will naturally manefest different responses to different circumstances. For example, when we encounter a rude person, we may feel anger, but when we encounter a kind person, we may feel love. Likewise, God may choose to display His wrath when confronted with sin and disobedience, or He may choose to display mercy and forgiveness. Either choice would be a legitimate responses to sin. God's lovingkindness and His burning wrath are two sides of His character and personality, and He may exhibit either one or the other as He pleases.
Fourth, God is bound by His own perfect nature. He must act in perfect ways. He cannot sin and He cannot lie, according to Scripture. Therefore, He must display His wrath against unrepentent sin and bring His judgment against those who have not received the atoning work of Christ. He cannot overlook sin or else He Himself commits an injustice. Conversely, God is just when He shows His favor to those who are justified by grace through faith Christ's sacrifice. So, God's own perfection will require He react in different ways under differnet circumstances.
Finally, God's personality is not disproportionately wrathful in the OT nor disproportionately merciful in the NT as some might claim. In reality, both the OT and NT testify equally to God's mercy and to His wrath. For example, in the OT God displays His anger against sinning Israelites at multiple points during their wanderings in the desert, yet He also showed His great mercy in sending Jonah to preach the Gospel to the city of Nineveh. In the NT, we see God's love and mercy in sending His Son to die for the sins of men, yet we also read in the letters of Paul, Peter and John about the coming judgment that awaits the unbelieving world (and the book of Revelation offers a detailed and chilling account of how God brings terrible judgments upon the world shortly before the return of Christ.)
Overall, some of the greatest examples of God's grace and mercy are evident in the OT (i.e., Joseph, the Exodus, Ruth, Esther, Jonah) while God's most terrifying displays of wrath and anger are described by Jesus in Matthew 24 and in the book of Revelation. Clearly, the Bible presents a balanced and nuanced perspective of a God Who possesses a full personality.
God does not contradict Himself when He chooses to show mercy to some people but wrath to others. Scripture teaches that God's wrath is the expected and appropriate response to sinful mankind under all circumstances, since we know the Bible teaches that no man does good and all are sinful (see Romans 3). Therefore when God shows mercy instead, it is truly grace (unmerited favor) made available as God chooses. He is under no obligation to ever extend mercy, yet in love He offers mercy to some for His own purposes. In keeping with God's perfect nature, God found a way to judge sin justly (i.e., upon Christ on the cross) while at the same time justifying the sinner through faith in the work of Jesus (see Rom 3:21-26).
The Bible teaches that God's grace is a matter of His sovereignty, and God owes no mercy to anyone. Simply put, God may display His wrath against some while showing mercy to others because God's sovereignty affords Him this right. Paul put it best in Romans 9:14-18:
When God is criticized for displaying His wrath in the OT, most of that criticism is centered on the time of Joshua and the Israelites entering the Promised Land. As a nation, Israel had entered into a covenant with God, which bound all of the nation to abide by God's standards of holiness (see Deut 29:10-15). In keeping with this covenant, God agreed to bring them into a land He would give them, but He commanded them to extinguish the sinners from the land to ensure the nation's holy status. The Israelites were to be God's instrument to execute His judgment against the sinners who occupied the land.
God is inherently just when He brings judgment against sin (once again, He owes no one mercy), and God is free to choose any means He wishes to carry out His judgments. In the time of Joshua, God chose to use Israel's army to carry out His judgment against the Canaanites. By contrast, God choose a supernatural means to judge Sodom and Gomorrah. Neither is inherently better or worse. God is free to choose any method that suits Him, and Israel was God's appointed instrument of judgment during the time of Joshua.
God commanded Israel to show no mercy to these inhabitants, because God had determined centuries earlier that the Canaanite people would not receive God's mercy in the day of Joshua. God told Abraham in Genesis 15:13-16 that these people were designated for judgment even before they had been born:
The Lord's mention of the Amorite is a reference to the Canaanites who were vanquished by Joshua. God said He would send Abraham's decedents outside the land for four hundred years, because God wasn't ready for the Canaanites to be judged. When that judgment was ready, however, God brought Israel into the land to become His instrument of judgment.
On the other hand, when God has not specifically given His people the decree to act as His instrument of judgment, we are not permitted to assume that role for ourselves. God instructed Israel to show mercy to other peoples when He choose to extend mercy rather than judgment. This is the essential difference between the OT and NT, though the principle can be seen equally in both places.
The best example of this pattern is seen when He commanded Jonah to preach a message of salvation to Israel's enemies in Nineveh. Jonah preferred to see the Ninevites judged, so he ran from God's presence and tried to force God's hand to judgment. Instead, God pursued Jonah and required him to preach a message of repentance leading to salvation. (Our ministry offers a comprehensive teaching on the story of Jonah and the way the Lord demonstrated His mercy in that day. You can find that teaching in our Jonah study.)
God's decision to use Israel as an messenger of His mercy and also an instrument of His wrath is the prerogative of a holy God. He has created all things to serve His purposes and to reflect His glory, and He may do as He wishes with His creation without respect to our preferences (See Roman 9 again).
We see this truth continue into the NT, when Jesus give commands to His disciples to never take vengeance or revenge against others. Instead, Jesus says we must forgive 70 times 7 and we must love our enemies. Furthermore, Paul taught:
Here we see God specifically prohibiting His people from taking judgment upon themselves. Rather, we are to leave all judgment to God. This is exactly the same pattern as in the book of Joshua. All judgment was left to God, though God chose to exercise His judgment through the army of Israel. Today, God has decreed that judgment is reserved for the day of Christ's return, so we are not free to act as judge in the meantime.
The difference between God's actions in Joshua's day and His actions today are a reflection of His prerogative as God and in keeping with His purposes to extend mercy and grace during this age. In the day of Joshua, God was intent on building up His people in Israel rather than extending mercy to the Gentiles nations. Today, God is extending mercy to the Gentiles nations in keeping with His promises to Abraham. (If you are interested in an in-depth teaching on God's plan for Israel and the Gentile nations, we encourage you to listen to chapters 9-11 of our Romans study).
God's nature and character includes both mercy and love together with anger and judgment against sin. God displays all sides of His personality consistently across both the Old and New Testaments. Furthermore, God is just when He displays His wrath against sin, but in mercy He chooses to show grace to some when He desires. This is the inherent right of a sovereign God. Finally, God used the nation of Israel to carry out His wrath against sinful nations, while today He has instructed the Church to refrain from judging. Ultimately, God reserves all judgment for Himself, and Scripture teaches that He intends to bring that judgment by His own hand in a future day.