God is love (1 John 4:8).
God is merciful (Exodus 34:6 and Deuteronomy 4:31).
God is faithful (1 Corinthians 1:9).
God is holy (Leviticus 11:44; 1 Peter 1:16; Psalm 77:13).
God is just (2 Thessalonians 1:6)
In the midst of persecution from members of their Greek society, Paul tells the Thessalonian Christians in his second letter written from Corinth in 52 AD, “God is just” (2 Thessalonians 1:6). And, because of this eternal character of God the Thessalonians can be assured that God “will pay back trouble to those who trouble you.” This is the same God who said three times (Exodus 21:24; Leviticus 24:20; Deuteronomy 19:21) in the Law he gave to Moses, “an eye for an eye.”
"Anyone who injures their neighbor is to be injured in the same manner: fracture for fracture, eye for eye, tooth for tooth. The one who has inflicted the injury must suffer the same injury." – Leviticus 24:20
The time for the Lord's justice will be "when the Lord Jesus is revealed form heaven in blazing fire with his powerful angels." It is at this time the penalty will be assigned and the punishment will begin to be imposed.
Isaiah captures this moment in his description of this future event in Isaiah 66:5-6. Through the prophet Isaiah, God explains to the people who "tremble at His word" 700 BC that the people of their own society who hate them, exclude them and mock them will be put to shame when the Lord comes to his temple to judge and punish his enemies with the punishment they deserve:
"Hear the word of the Lord, you who tremble at his word: 'Your own people who hate you, and exclude you because of my name, …they will be put to shame. Hear that uproar from the city, hear that noise from the temple! It is the sound of the Lord repaying his enemies all they deserve.' " – Isaiah 66:5-6
Isaiah speaks of the day the Lord appears in his Temple, which is the same day spoken of by Paul when he says,
"This will happen when the Lord Jesus is revealed from heaven in blazing fire with his powerful angels. He will punish those who do not know God and do not obey the gospel of our Lord Jesus." – Second Thessalonians 1:8