In John's gospel, one of the earliest teachings of Christ is reaffirming the reality of the wrath of God. In 3:36, Jesus states. He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him. There is a common belief that the New Testament is not like the Old, that the wrathful God of the prophets was not the same Father of Jesus. This misbelief is patently false, and abundantly disproven throughout the New Testament, including from Jesus' mouth directly.
To question the wrath of God is not particularly unwise. Even Moses contended with it. The wrath of God is first questioned (in the King James Bible anyhow) by Moses in Exodus 32:11. Lord, why doth thy wrath wax hot against thy people, which thou hast brought forth out of the land of Egypt with great power, and with a mighty hand? The answer to the question is the sin of idolatry. Moses had gone to commune with God, and in that time, the people had already turned to false pagan demons. We see that God's wrath is provoked in the same way every time: when people reject God's truth for falsehood and idolatry. God's wrath is the same in the Old and New Testaments, as the Old and New Testaments depict the exact same person as God, with the exact same character. Incidentally, the name of the two earliest heresies that asserted that the Old and New Testaments depicted different Gods are Marcionism and Gnosticism. This is an old belief, and rejected by the church at an early date.
In Psalm 59, David explicitly entreats God to pour out his wrath not in taking life, but in humiliating God's enemies. David writes in verses 11 to 15. Slay them not, lest my people forget: scatter them by thy power; and let them know that God ruleth in Jacob unto the ends of the earth. Selah. And at evening let them return; and let them make a noise like a dog, and go round about the city. Let them wander up and down for meat, and grudge if they be not satisfied. It is within the realm of acceptable prayer to ask God to bring His wrath to bear on His enemies!
The prophet Nahum characterizes God's wrathful nature very early in his account, immediately after the first verse which contains the attribution. The second and third verses state. God is jealous, and the Lord revengeth; the Lord revengeth, and is furious; the Lord will take vengeance on his adversaries, and he reserveth wrath for his enemies. The Lord is slow to anger, and great in power, and will not at all acquit the wicked: the Lord hath his way in the whirlwind and in the storm, and the clouds are the dust of his feet.
John's gospel is known as a bit of an outlier as far as gospel accounts go. I believe that John's account was compiled explicitly as a supplement and keystone to the others. Nevertheless, both Matthew and Luke's accounts also recount Christ talking about the wrath of God, and in exactly the same location, 3:7. Christ speaks to the multitude (Luke's term) which comprised Pharisees and Sadducees (Matthew's terms). O generation of vipers, who hath warned you to flee from the wrath to come? Christ here was speaking about his prophecy that the temple would be destroyed, and the people of Judea scattered. This is an explicit fulfilment of David's prayer before! When you pray perfectly aligned with God's will, your prayers have no choice but to happen!
Luke records Christ speaking of God's wrath one more time. Jesus is speaking of what is understood as the end times in chapter 21. Verses 22 and 23 state. For these are the days of vengeance, that all things which are written may be fulfilled. But woe unto them that are with child, and to them that give suck, in those days! for there shall be great distress in the land, and wrath upon this people.
Not only does this depict the sacking of the temple, but also the forthcoming tribulation recorded in the Revelation of John. Beware! The wrath of God is coming. In Revelation 14:8, an angel explains. Babylon is fallen, is fallen, that great city, because she made all nations drink of the wine of the wrath of her fornication. So we see that the final wrath of God is contingent upon the behaviour of fornication!
In his letters, Paul speaks of wrath more than all the other books of the New Testament combined, and nowhere is the discussion of wrath more pointed than in Romans. If you're interested in further characterizing God's wrath, read the first two chapters of Romans, but I'll excerpt a bit here. First, Paul writes in 1:18. For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness. So, first, Paul explains how God sees that which invokes His wrath. For the sake of brevity, I will skip over the passage that links this wrath to sexual deviancy and fornication, consistent with the Revelation passage.
Next, Paul depicts the causes of wrath from the human side in chapter 2 verse 5. But after thy hardness and impenitant heart treasurest up unto thyself wrath against the day of wrath and revelation of the righteous judgment of God. Skipping two verses describing the blessed saints, Paul returns to documenting the characters of men that elicit the wrath of God in verses 8 and 9. But unto them that are contentious, and do not obey the truth, but obey unrighteousness, indignation and wrath, tribulation and anguish, upon every man that doeth evil, of the Jew first, and also of the Gentile.
Paul discusses the endgame of God's wrath in 9:22. What if God, willing to shew his wrath, and to make his power known, endured with much longsuffering the vessels of wrath fitted to destruction? God is infinitely just, and in his great justice, must judge with wrath those who commit evil. Christians are not supposed to be vessels of God's wrath, but rather his love, and so to balance this out, God reserves all the wrath and judgment for himself. No one else can justly adjudicate it. Paul reifies this in 12:19. Dearly beloved, avenge not yourselves, but rather give place unto [God's] wrath: for it is written, (here he cites Deuteronomy 32:35) Vengeance is mine; I will repay.
Paul's framing in the opening of Ephesians 2 works well enough as a benediction and conclusion, placing all the framing of God's wrath together with the gospel. And you hath he quickened, who were dead in trespasses and sins; Wherein in time past ye walked according to the course of this world, according to the prince of the power of the air, the spirit that now worketh in the children of disobedience: Among whom also we all had our conversation in times past in the lusts of our flesh, fulfilling the desires of the flesh and of the mind; and were by nature the children of wrath, even as others. But God, who is rich in mercy, for his great love wherewith he loved us, Even when we were dead in sins, hath quickened us together with Christ, (by grace ye are saved;) And hath raised us up together, and made us sit together in heavenly places in Christ Jesus: That in the ages to come he might shew the exceeding riches of his grace in his kindness toward us through Christ Jesus.
Postscript: In a reading of Isaiah, I came across an even better benediction than Paul's! Isaiah writes in 35:3,4. Strengthen ye the weak hands, and confirm the feeble knees. Say to them that are of a fearful heart, Be strong, fear not: behold, your God will come with vengeance, even God with a recompence; he will come and save you.