“As therefore the tares (darnel) are gathered up and burned with fire, so will it be in the end of the world (age). The Son of man will send forth his angels, and they will gather out of his kingly rule all things that cause stumbling, and those who do iniquity,”
Thus just as at the harvest the false wheat, the darnel, had to be gathered up and burned with fire because it was useless except for fuel, so in the same way at the end of the age the Son of Man will act to purify the sphere of His Kingly Rule. His Kingly Rule will have been established worldwide (Daniel 7:13-14), and the sphere of His Kingly Rule must now be purified. So the One Who originally sowed the seed and began the process, will send His angels to gather out from the sphere of His Kingly Rule all that causes stumbling and offence to others, and all who do iniquity. Note the assumed fact of the present and continuing Kingly Rule of the Son of Man (‘out of His kingly rule'). But we are not to see the idea here as that of a chronological ‘order of events', as though we can say ‘this happens first, and then that'. It is rather laying the emphasis on the restoration of Paradise to what its should be. It is confirming that there will be a removal of all that is evil leaving only the good. Paradise (Isaiah 11:1-9) will be restored.
‘They will gather out of His Kingly Rule.' The Kingly Rule is the Lord's and He is ruler over the nations' (Psalms 22:28). For ‘the Lord has established His throne in the heavens, and His Kingly Rule reigns over all' (Psalms 103:19). ‘And to Him (the Son of Man) was given dominion and glory and a kingly rule, that all the peoples and nations and languages should serve Him' (Daniel 7:14). Thus the Kingly Rule is universal, and the world is here in mind. Compare also the quotation in Matthew 13:14-15 which in its context in Isaiah had in mind the revelation of the Kingship of the LORD, again in a context of heavenly beings (Isaiah 6:1-6).
The use of angels in this task and at the consummation of all things is one that is continually mentioned. See Matthew 13:49; Matthew 16:27; Matthew 24:31; Matthew 25:31; Mark 13:27; and note their mention in connection with the Kingly Rule in Psalms 103:20.
For ‘all things that cause stumbling, and those who do iniquity (lawlessness)” compare Zephaniah 1:3, ‘the stumblingblocks with the wicked'. Both what causes sin, together with sinners themselves, will be removed from interfering with God's people in the new Paradise. All that is unsavoury will be excluded (Revelation 21:27).