God’s fury against sin is held back by His long suffering. It is only His mercy that restrains the lightning of His wrath. Our God is a consuming fire (see Heb. 12:29). See also Zech. 2:5 comment. See also Deut. 10:16 comment regarding circumcision of the heart.
“It is because God’s wrath is real that His mercy is relevant. Unless you have a real wrath, a real anger, the biblical concepts of long-suffering, of mercy, and of grace are robbed of their meaning.” Allister Begg
Jeremiah 4:4 Circumcise yourselves to the Lord, And take away the foreskins of your hearts, You men of Judah and inhabitants of Jerusalem, Lest My fury come forth like fire, And burn so that no one can quench it, Because of the evil of your doings.