ISB ~ Matthew 3 v2

kingdom of heaven:The overarching theme of Matthew’s Gospel. The expression appears 32 times in the Gospel and is equivalent in meaning to “the kingdom of God” (see, e.g., 19:23-24). In their original Jewish context, the words “of heaven” helped to distinguish the kingdom proclaimed by John (3:2) and Jesus (4:17) from popular hopes for a literal restoration of Israel’s political empire (cf. Acts 1:6). Instead, it is a kingdom that comes from the Father in heaven (Mt 6:10). The presence of the kingdom is mediated through the Church in history (16:18-19); its full manifestation, however, awaits the coming of Christ in glory (25:31-46) (CCC 541, 669-71).

See introduction to Matthew:Themes.