25 What then follows? “The loftiest hills are for the stags”. The stags are mighty, spiritual, passing in their course over all the thorny places of the thickets and woods. “He makes my feet like harts' feet, and sets me up on high.” Let them hold to the lofty hills, the lofty commandments of God; let them think on sublime subjects, let them hold those which stand forth most in the Scriptures, let them be justified in the highest: for those loftiest hills are for the stags. What of the humble beasts? What of the hare? What of the hedgehog? The hare is a small and weak animal: the hedgehog is also prickly: the one is a timid animal, the other is covered with prickles. What do the prickles signify, except sinners? He who sins daily, although not great sins, is covered over with the smallest prickles. In his timidity he is a hare: in his being covered with the minutest sins, he is a hedgehog: and he cannot hold those lofty and perfect commandments. For “the loftiest hills are for the stags.” What then? Do these perish? No. For so “is the rock the refuge for the hedgehogs and the hares.” For the Lord is a refuge for the poor. Place that rock upon the land, it is a refuge for hedgehogs, and for hares: place it on the sea, it is the home of the coot. Everywhere the rock is useful. Even in the hills it is useful: for the hills without the rock's foundation would fall into the deep....
26. “He appointed the Moon for certain seasons”. We understand spiritually the Church increasing from the smallest size, and growing old as it were from the mortality of this life; yet so, that it draws nearer unto the Sun. I speak not of this moon visible to the eye, but of that which is signified by this name. While the Church was in the dark, while she as yet appeared not, shone not forth as yet, men were led astray, and it was said, This is the Church, here is Christ; so that “while the Moon was dark, they shot their arrows at the righteous in heart.” How blind is he who now, when the Moon is full, wanders astray? “He appointed the Moon for certain seasons.” For here the Church temporarily is passing away: for this subjection to death will not remain for ever: there will some time be an end of waxing and waning; it is appointed for certain seasons. “And the sun knows his going down.” And what sun is this, but that Sun of righteousness, whom the ungodly will lament on the day of judgment never having risen for them; they who will say on that day, “Therefore we wandered from the way of truth, and the light of righteousness shone not on us, and the sun did not arise upon us.” That sun rises for him who understands Christ....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)