For he hath founded it upon the seas. The Psalmist here confirms the truth, that men are rightfully under the authority and power of God, so that in all places and countries they ought to acknowledge him as King. And he confirms it from the very order manifested in the creation; for the wonderful providence of God is clearly reflected in the whole face of the earth. In order to prove this, he brings forward the proof of it, which is most evident. How is it that the earth appears above the water, but because God purposely intended to prepare a habitation for men? Philosophers themselves admit, that as the element of the water is higher than the earth, it is contrary to the nature of the two elements for any part of the earth to continue uncovered with the waters, and habitable. Accordingly, Job (Job 28:11, 25) extols, in magnificent terms, that signal miracle by which God restrains the violent and tempestuous ragings of the sea, that it may not overwhelm the earth, which, if not thus restrained, it would immediately do and produce horrible confusion. Nor does Moses forget to mention this in the history of the creation. After having narrated that the waters were spread abroad so as to cover the whole earth, he adds, that by an express command of God they retired into one place, in order to leave empty space for the living creatures which were afterwards to be created, (Genesis 1:9) From that passage we learn that God had a care about men before they existed, inasmuch as he prepared for them a dwelling-place and other conveniences; and that he did not regard them as entire strangers, seeing he provided for their necessities, not less liberally than the father of a family does for his own children. David does not here dispute philosophically concerning the situation of the earth, when he says, that it has been founded upon the seas. He uses popular language, and adapts himself to the capacity of the unlearned. Yet this manner of speaking, which is taken from what may be judged of by the eye, is not without reason. The element of earth, it is true, in so far as it occupies the lowest place in the order of the sphere, is beneath the waters; but the habitable part of the earth is above the water, and how can we account for it, that this separation of the water from the earth remains stable, but because God has put the waters underneath, as it were for a foundation? Now, as from the creation of the world, God extended his fatherly care to all mankind, the prerogative of honor, by which the Jews excelled all other nations, proceeded only from the free and sovereign choice by which God distinguished them.

For he hath founded it upon the seas - That is, the earth, or the habitable world. The ground of the claim to the earth and all that it contains, which is here asserted, is the fact that God had created it, or "founded" it. The language used here - "he hath founded it," that is, he has laid the foundation of it, "upon the seas" and "the floods" - is in accordance with the usual mode of speaking of the earth in the Scriptures as laid upon a foundation - as a house is raised on a firm foundation. See the notes at Job 38:6. As the earth appeared to be surrounded by water, it was natural to speak of it as "founded" also upon the waters. There is probably an allusion here to the statement in Genesis 1:9-10, where the waters are said to have been so gathered together that the dry land appeared. Above all the waters the earth was established, so as to become the abode of plants, animals, and man.
And established it upon the floods - The streams; the torrents. The earth has been elevated above them, so as to be a residence for animals and for men. The essential thought is, that this earth has become what it is by the fact that God has founded it; and, therefore, what it produces belongs of right to Him.

He hath founded it upon the seas - He not only created the vast mass, but separated the land from the waters, so that the mountains, etc., being elevated above the waters, appear to be founded on them, and notwithstanding all the tossings and ragings of the ocean, these waters cannot prevail. It is established upon the floods, and cannot be shaken.

For he hath founded it upon the (a) seas, and established it upon the floods.
(a) He notes two things: the one, that the earth to man's judgment seems above the waters: and next, that God miraculously preserves the earth, that it is not drowned with the waters, which naturally are above it.

For he hath founded it upon the seas,.... Or "with" them, as some interpret (e) the particle he hath founded the earth and seas together, and both upon nothing; and yet are stable and firm; or "by the seas" (f), near unto them, at the side of them; which, though higher than the earth, are wonderfully bounded by the power of God, so as not to return and cover the earth; see Job 38:8; so the particle is used in Psalm 1:3. Some have thought that the first earth, which Peter says was standing in the water, and out of the water, 2-Peter 3:5, was made in the form of an egg, and that the waters were under the earth, and the earth was as a crust or shell over them, until the deluge came; and this crust then broke in, and formed the sea; and so it was literally true, that the earth was founded upon, or over the waters;
and established it upon the floods; the floods of the seas, or rivers of water running to and fro in it: this shows the ground and foundation of Christ's right and claim to the earth, and all that is in it; which is not by reason of his father's gift to him as Mediator, but by virtue of his concern in creation, the world, and all things in it, being made and established by him; in him do all things consist, Colossians 1:16.
(e) R. Moses in Aben Ezra in loc. (f) "juxta maria", Vatablus, Gejerus, Amama; so Kimchi & Ben Melech.

Poetically represents the facts of Genesis 1:9.

Seas - The whole collection of waters, as well as the sea and the rivers running into it, as that great abyss of waters which is contained in the bowels of the earth.