Question: Why does is seem like the God of the Old Testament is much more harsh than the God of the New Testament? (For example: The flood wipes out all people but one family; God kills all the first born in Egypt; The Israelites are told to kill entire populations in Canaan; and the death penalty is demanded for several offenses in the Levitical Law.)

Many people have espoused views similar to those described above. The following quote is from Richard Dawkins in his book The God Delusion (p.31). He says that the God of the Old Testament is “arguably the most unpleasant character in all fiction: jealous and proud of it, a petty, unjust, unforgiving control-freak; a vindictive, bloodthirsty ethnic cleanser; a misogynistic, homophobic, racist, infanticidal, genocidal, filicidal, pestilential, megalomaniacal, sadomasochistic, capriciously malevolent bully.”

Answer: God is not more harsh in the Old Testament than in the New Testament. God is just, and must judge those who sin against Him. In every example mentioned above, God is judging the sin of human beings. Paul says: “For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who suppress the truth in unrighteousness” (Romans 1:18). God is just as serious about sin in the New Testament as He is in the Old Testament.
Compare the following from the Old and New Testaments:
Old Testament

Ezekiel 18:20 – “The soul who sins shall die.”
Isaiah 3:11 – “Woe to the wicked! It shall be ill with him, For the reward of his hands shall be given him.”
Psalm 37:20 – “But the wicked shall perish; And the enemies of the LORD, Like the splendor of the meadows, shall vanish. Into smoke they shall vanish away.”

New Testament

Romans 6:23 – “For the wages of sin is death.”
1 Corinthians 6:9-10 – “Do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived. Neither fornicators, nor idolaters, nor adulterers, nor homosexuals, nor sodomites, 10 nor thieves, nor covetous, nor drunkards, nor revilers, nor extortioners will inherit the kingdom of God.”

Yet there is one thing in particular that can help us to understand why the Old Testament records God’s involvement in the particular physical judgment of certain groups of people throughout that period of history.
Keep in mind that the Old Testament covers a much longer period of history than the New Testament. (Over 4,000 years compared to less than 100 years!) From the very beginning of the Old Testament, following the fall into sin, God had promised to send the world a Savior from sin and God’s just judgment against sin. While God repeatedly demonstrates patience toward sinners throughout the Old Testament, God was also acting in history to preserve a remnant of His faithful people in the Old Testament, from which the promised Savior would eventually be born. Throughout the Old Testament God gives us a “behind the scenes” view of His actions in history. Here God describes His work through the lives of people and nations, to judge sin and to preserve a particular people through which He would fulfill His promise of redemption, for the benefit of all people. This difference in time and perspective is the reason why God “seems” to be more harsh in the pages of the Old Testament.
Examples of God’s judgment in the Old Testament

• The flood wipes out all people but one family – Genesis 6:5
• Destruction of Sodom and Gomorrah – Genesis 18:20
• God kills all first born in Egypt – Exodus 1:8-22
• The death penalty for several offenses in the Levitical Law – Leviticus 20:2,9,10-16,27; Deuteronomy 13:10-11
• Israelites kill entire populations in Canaan – Deuteronomy 7:1-5; 20:16-18; Joshua; Judges; (Compare Genesis 15:16; Leviticus 18:2-30)

God is just as unhappy with sin today as he was in the days of Noah (the flood), Lot (destruction of Sodom and Gomorrah) and Moses (destruction of nations), and sin still brings God’s just judgment. (Compare the death of Herod in Acts 12:23: “Then immediately an angel of the Lord struck him, because he did not give glory to God. And he was eaten by worms and died.”) We are all under the death penalty because of our disobedience to God’s laws. At the same time, God is also merciful and has provided a means of salvation for all people in the person of Jesus Christ. Both the Old and the New Testaments are clear about this as well.
Old Testament

Isaiah 52:10 – “Indeed He says, ‘It is too small a thing that You should be My Servant To raise up the tribes of Jacob, And to restore the preserved ones of Israel; I will also give You as a light to the Gentiles, That You should be My salvation to the ends of the earth.’”

New Testament 

1 John 4:9 – “In this the love of God was manifested toward us, that God has sent His only begotten Son into the world, that we might live through Him.”

The God of the Old and New Testaments are one and the same. While the LORD is just and demands that our sin receive its just punishment, He is also merciful, and desires the salvation of every sinner. This He has accomplished by His grace in the person and work of Jesus, and His gift of salvation and eternal life becomes ours through faith in Him. Yes, God hates sin, but He loves the sinner, and He has demonstrated that in Jesus.