Albert Barnes Commentary Psalms 89:11

"The heavens are thine, the earth also is thine: The world and the fulness thereof, thou hast founded them." — Psalms 89:11 (ASV)

The heavens are yours - Are your work; and, therefore, your property - the highest conception of property being that which is derived from creation. It is also implied here that as all things belong to God, he has a right to dispose of them as he pleases.

The earth also is yours - The earth itself, as made by you; all that the earth produces, as having sprung out of that which you have made. The entire proprietorship is in you.

As for the world - In the use of this word, the earth is spoken of as inhabitable, meaning that the earth and all that dwell upon it belong to God.

And the fullness of it - All that it produces; what constitutes its entirety. That is, the earth itself considered as earth, or as a mass of matter; and all that springs from it; all that constitutes the earth, with all its mountains, seas, rivers, people, animals, minerals, harvests, cities, towns, monuments - the productions of nature, the works of power, and the achievements of art. Compare the notes at Psalms 24:1.

You have founded them - They all have their foundation in you; that is, you have caused them all to exist. They have no independent and separate basis on which to rest.