Pseudo-Chrysostom on Mark 1:14-15
But the kingdom of God is essentially the same as the kingdom of heaven, though they differ in idea. For by the kingdom of God is to be understood that in which God reigns; and this in truth is in the region of the living, where, seeing God face to face, they will abide in the good things now promised to them; whether by this region one chooses to understand Love, or some other confirmation of those who put on the likeness of things above, which are signified by the heavens. For it is clear enough that the kingdom of God is confined neither by place nor by time.
Pseudo-Chrysostom on 6:32
The kingdom of God is the reward of good works; His righteousness is the way of piety by which we go to that kingdom.



Theophylact on Matt. 3:2
The kingdom of heaven means the first and second comings of Christ, and also the virtuous life. For when we walk on earth as if we lived in heaven, not living according to the passions, then we possess the kingdom of heaven.
Theophylact on Matt 6:32
The kingdom of God is the enjoyment of all that is good. This comes through righteousness. To him who seeks after spiritual things God in His generosity adds that which is needed for physical life.




Theophylact On Mark 1:14-15
from this time the kingdom of God will work, that is, a conversation according to the Gospel, which is with reason likened to the kingdom of heaven. For when you see a man clothed in flesh living according to the Gospel, do you not say that he has the kingdom of heaven, which is not meat and drink, but righteousness and peace and joy in the Holy Ghost?


St. Regimus on Matthew 3:2
The Kingdom of Heaven has a fourfold meaning. It is said, of Christ, as The Kingdom of God is within you (Luke 17:21). Of Holy Scripture, as, The Kingdom of God shall be taken from you, and shall he given to a nation bringing forth the fruits thereof (Mat 21:43). Of the Holy Church, as, The Kingdom of Heaven is like to ten virgins (Mat 25). Of the abode above, as, Many shall come from the East and the West, and shall sit down in the Kingdom of Heaven (Mat 8:11). And all these significations may be here understood.




St. Clement of Alexandria Fragment 17
The kingdom of Heaven? This refers to justification by faith and sanctification by the Spirit. This is why it says elsewhere, 'the kingdom of heaven is within you." (Lk 3:1-2)

St. John Chrysostom on Matt 3:2
But by the kingdom in this place he means His former and His last advent.