Augustine of Hippo

"And the fountains of water were seen. And the fountains of water springing up into everlasting life," which were made in the preachers, were seen. "And the foundations of the round world were revealed." And the Prophets, who were not understood, and upon whom was to be built the world of believers in the Lord, were revealed. "At Thy chiding, O Lord:" crying out, "The kingdom of God is come nigh unto you." "At the blasting of the breath of Thy displeasure;" saying, "Except ye repent, ye shall all likewise perish."

Exposition on Psalm 18 ↗

Thomas Aquinas

"And the fountains appeared." Here he treats of the generation of waters, which emanate from certain sources called springs, from which all generation of waters comes. Now these are generated in two ways. Sometimes from a customary and natural cause: just as vapors are raised above the earth and from this elevation are cooled above and descend and become rains, so also from the interior heat of the earth, when vapors do not exit, they collect and are resolved into water and become springs of water. …

Exposition on the Psalms of David ↗