The domain of God.
The presence of God.
The rule of God.
Heaven’s has come
“3 How blessed are the poor in spirit: the kingdom of Heaven is theirs.” Gospel according to st. Matthew- chapter 5; New Jerusalem Bible
“4:17. From that time Jesus began to preach, and to say: Do penance, for the kingdom of heaven is at hand.
Exinde coepit Iesus praedicare et dicere paenitentiam agite adpropinquavit enim regnum caelorum” Matthew chapter 4 verse 17 Douay Rheims bible
The Kingdom of heaven is not considered as something that is only to come, but is already here on earth, and strengthening (Matthew chapter 3 verses 1 and 2, Ps 145:10-11, 12-13, 17-18, Lk 10:1-9, Lk 17:20-25, Isaiah chapter 9 Verse 7, Book of Luke - Chapter 13 verses 18 to 30, John chapter 3 verse 3, Matthew 19 verse 12 and 29,Mattew 23 v 13).
It manifests itself in the Catholic Church( I Collosians chapter 1 v 3, 16-18, 24, 26, 28 ; I Corinthians chapter 15 verses 24, 25 ,26, 50,I Timothy chapter 3 verse 15, Ephesians 5 verse 24).
“669 As Lord, Christ is also head of the Church, which is his Body.551 Taken up to heaven and glorified after he had thus fully accomplished his mission, Christ dwells on earth in his Church. The redemption is the source of the authority that Christ, by virtue of the Holy Spirit, exercises over the Church. “The kingdom of Christ [is] already present in mystery”, “on earth, the seed and the beginning of the kingdom”.552
670 Since the Ascension God’s plan has entered into its fulfillment. We are already at “the last hour”.553 “Already the final age of the world is with us, and the renewal of the world is irrevocably under way; it is even now anticipated in a certain real way, for the Church on earth is endowed already with a sanctity that is real but imperfect.”554 Christ’s kingdom already manifests its presence through the miraculous signs that attend its proclamation by the Church.” CCC
The church is the kingdom of heaven on earth ( see quotes above). It is eternal, neither can it’s doctrine change(I Corinthians 15 verses 1 to 3), nor can its substance change(I Corinthians 15 verse 50), nor can it cede to corruption(Psalm 16 verse 10), nor can it ever loose it’s authority - doctoral (I Timothy chapter 3 verse 15), or physical (Luke 9;1 Corinthians 5;). It is protected and ruled by God (Ephesians 1 v 11-15;Matthew 16 verses 17- 20). This, despite the fact that the members of the church themselves are less perfect.
Safeguard of truth
The church is the safeguard of the truth, and defender of the Gospel (Acts 15;I Timothy chapter 3 verse 15). She is the final Authority on scripture, and cannot be judged by the world’s standards.
St. Mathew and heaven
The Gospel of Matthew is largely focussed on showing the kingdom of heaven is already come.
Taste of heaven
The church is a taste of heaven.