an emotion of instant displeasure
Anger is part of our original human nature, just as LOVE is. It is not necessarily sinful. It becomes sinful when it rises without cause or is excessive or protracted.
Be angry, and yet do not sin; do not let the sun go down on your anger… —Ephesians 4:26 NASB
…put them all aside: anger, wrath, malice, slander, and abusive speech from your mouth. —Col. 3:8 NASB
But I say to you that everyone who is angry with his brother shall be guilty before the court; and whoever says to his brother, ‘You good-for-nothing,’ shall be guilty before the supreme court; and whoever says, ‘You fool,’ shall be guilty enough to go into the fiery hell. —Matthew 5:22 NASB
God has anger. This is not a sin, but is merely a result of His righteous displeasure with sin and sinners.
God is a just judge, And God is angry with the wicked every day. —Psalms 7:11 NKJV
NASB: God is a righteous judge,
And a God who has indignation every day.