Matthew 3:2 - Coke's Commentary on the Holy Bible

Repent ye— This was only the substance and result of his preaching. The kingdom of heaven and the kingdom of God, are but two phrases for the same thing, agreeably to the style of the Hebrews; who frequently used the word heaven to denote God himself who dwells there. Hence what is here called by St. Matthew the kingdom of heaven, is by St. Mark and St. Luke called the kingdom of God; Mark 1:15.Luke 6:20. The kingdom of heaven, therefore, signifies here the kingdom of God, which was founded and established by the Lord Jesus Christ,—the kingdom of grace here, introductory to the kingdom of glory hereafter; and this expression is founded on Daniel 2:44; Daniel 7:13-14. Now, as the kingdom of heaven was to be opened by the preaching of the Gospel, John the Baptist rightly says, that it was at hand; since the Lord Jesus Christ entered on his public ministry about six months after. See Luke 3:2-3. The demand of repentance shewed that this was a spiritual kingdom, and that no wicked man, how politic or brave, how learned or renowned soever, could possibly be a genuine member of it. See Whitby, Beausobre and Lenfant, Doddridge, and Heylin, p. 19. For the next verse we refer to the notes on Isaiah 40:3.