11 Therefore the Prophet says unto these great and small, the mountains and the little hills, the rams and the young sheep, what follows: “You are the blessed of the Lord, who made heaven and earth”. As if he should say, You are the blessed of the Lord, who made the heaven in the great, earth in the small: not this visible heaven, studded with luminaries which are objects to these eyes. For “The heaven of heavens is the Lord's”; who has elevated the minds of some saints to such a height, that they became teachable by no man, but by God Himself; in comparison of which heaven, whatever is discerned with carnal eyes is to be called earth; which “He has given to the children of men;” that when it is contemplated, whether in that region which illumines above, as that which is called heaven, or in that which is illumined beneath, which is properly called earth (since in comparison with that which is called heaven of heaven, the whole, as we have said, is earth;) the whole therefore of this earth He has given to the children of men, that by the consideration of it, as far as they can, they may conceive of the Creator, whom with their yet weak hearts they cannot see without that aid to their conception.
12....But nevertheless since they derive the truth and richness of wisdom, not from man nor through man, but through God Himself, they have received little ones who shall be heaven, that they may know that they are heaven of heaven; as yet however earth, unto which they say, “I have planted, Apollos watered, but God gave the increase.” For to those very sons of men whom He made heaven, He who knows how to provide for the earth through heaven, has given earth upon which they work. May they therefore abide, heaven and earth, in their God, who made them, and let them live from Him, confessing unto Him, and praising Him; for if they choose to live from themselves, they shall die, as it is written, “From the dead, as though he were not, confession ceases.” But, “The dead praise not You, O Lord, neither all they that go down into silence”. For the Scripture in another passage proclaims, “The sinner, when he comes into the abyss of wickednesses, scorns.” “But we, who live, will praise the Lord, from this time forth for evermore”.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)