‘And to you who are afflicted rest with us at the revelation of the Lord Jesus from Heaven, with the angels of his power, in flaming fire, rendering vengeance to those who do not know God, and to those who do not obey the Gospel of our Lord Jesus.'
The thought continues. When the Lord Jesus is revealed from Heaven in a full revelation of what He is (apokalupsis), with ‘the angels of His power', that is with the angels who exercise His authority and carry out His powerful commands, as so often promised (Matthew 16:27; Matthew 13:41-42; Mark 8:38), his own afflicted ones will be relieved from tension (like a bow string slackened from the bow), they will ‘rest' with Him. The battle will be over. Their afflictions will no longer be important. Paul joins himself and his companions with them in the thought. They will all be there together at rest. They will have ‘entered into their rest' (Hebrews 4:1; Hebrews 4:9).
What this rest involves is described in 1 Thessalonians 4:13-18 and in Matthew 13:43. The angels are involved in that too (Matthew 24:31). They will be gathered from the four winds and will shine like the sun in the Kingdom of their Father. As a result of their ‘taking away' at the time of His revelation of Himself they will be ‘ever with the Lord', resting in His presence. But that ‘revelation' (revealing in His fullness) of the Lord Jesus will be very different for the unbeliever, for He and His angels will come in flaming fire (Matthew 13:42; Matthew 13:50) rendering vengeance on those who had refused to know and acknowledge Him (Romans 1:28), and had therefore refused to obey Him and respond to His message of Good News.
Note that Matthew 13:41-43; Matthew 13:48-50 indicate the parallel results of the one activity. It could not be clearer. The angels will gather out all that offends, like the weeds are gathered up from the field, and the righteous will shine forth as the sun in the Kingdom of their Father. Note that in Matthew 13:48 ‘they gathered the good into pots, but the bad they cast away'. This is then interpreted as ‘the angels shall come forth and sever the wicked from among the just'. The gathering of only the good into pots means that by that the wicked have been severed, just as by the taking away of His people Jesus has severed the evil from among them. Compare also Matthew 25:31-46 where the consequences of the judgment are eternal for both types of participant (Matthew 25:46). Both the just and the unjust are dealt with around the same time at the coming of Jesus Christ Compare John 5:29.
‘From Heaven.' While on earth He was the Son of man who came down from Heaven (John 3:13), but His glory was veiled except at the Transfiguration (see Matthew 17:2). Now He is fully revealed in all His glory from Heaven, as the Heavenly One.
‘In flaming fire.' This may refer to the appearance of His glory (Exodus 3:2; Isaiah 66:15; Ezekiel 1:27; Revelation 1:14-15) or to the awfulness of His judgment (Hebrews 10:27; 2 Peter 3:7; 2 Peter 3:10). Or indeed both, in the sense that His flame will appear and will devour them (Hebrews 12:29). Compare Isaiah 2:10; Isaiah 2:19; Isaiah 2:21.
‘Taking vengeance.' Compare Revelation 6:9-10; Psalms 79:10; Psalms 119:84; Romans 2:5. The idea, as in 2 Thessalonians 1:6, is that those who have persecuted His people and have revelled in sin will receive according to what they have sown (Galatians 6:8). What they have done, so will be done to them. But it is not pure revenge, it is the just punishment of which they are worthy. Vengeance belongs to God (Romans 12:19; Deuteronomy 32:25), and He repays justly (compare how the leaders of Israel passed judgment on themselves without being aware of it, acknowledging the rightness of it - Matthew 21:41). Thus the One Who rightly takes vengeance is exercising the prerogative of God.
‘Who do not know God -- who obey not the Gospel'. Compare Psalms 79:6; Romans 1:28; John 3:36. They refuse to know, they refuse to obey. Notice that to know God and to obey the Gospel are in parallel. Those who know God will obey the Gospel. And what is that Good News? It is the Lord Jesus Himself. It is His Good News and it points to Him.