32 Listen for your confirmation in hope, for your security, if you know yourself to be among the members of Christ. “I have sworn once by My holiness that I will not lie unto David”. Do you wait till God swear a second time? How often is He to swear, if in one oath He is false? One oath He made for our life, who sent His Only One to die for us. “I have sworn once by My holiness, that I will not lie unto David.” “His seed shall endure for ever”. His seed endures for ever; because the Lord knows them that are His.
“And His seat is like as the sun before me:” “and as the moon perfect for evermore: and the faithful witness in heaven”. They are His seat, in whom He sits and reigns. But if His seat, His members also; because even our members are the seat of our head. See how all our other members sustain our head: but the head supports nothing above itself, but is itself supported by the rest of our limbs, as if the whole body of a man were the seat of his head. His seat, therefore, all in whom God reigns, “shall be like as the sun before Me,” He says: because the righteous in the kingdom of My Father “shall shine like the sun.” But the sun is meant in a spiritual, not a bodily sense, as that which shines from Heaven, which He makes to rise upon the just and unjust. Finally, that sun is not before men's eyes only, but even those of cattle and the smallest insects; for which of the vilest animals sees not that sun?
What does he say to distinguish the sun meant here? “Like as the sun before Me.” Not before men, before the flesh, before mortal animals, but “before Me, and as the moon.” But what moon? One “that is perfect for evermore.” For although that moon which we know becomes perfect, the next day she begins to wane, after her orb is full. “He shall be as the moon perfect for evermore,” He says. His seat shall be made perfect as the moon, but that moon is one which will be perfect for evermore.
If as the sun, why also as the moon? The Scriptures usually signify by the moon the mortality of this flesh, because of its increasings and decreasings, because of its transitory nature. The moon is also interpreted as Jericho: one who was descending from Jerusalem to Jericho fell among robbers: for he was descending from immortality to mortality. Similar then is the flesh to that moon, which every month suffers increase and decrease: but that flesh of ours will be perfect in the resurrection: “and a faithful witness in heaven.”
Thus then, if it was our mind only that would be perfected, he would compare us only to the sun: if our body only, to the moon; but as God will perfect us in both, in respect of the mind it is said, “like as the sun before Me,” because God only sees the mind: and “as the moon,” so is the flesh: which “shall be made perfect for evermore,” in the resurrection of the dead: “and a faithful witness in Heaven,” because all that was asserted of the resurrection of the dead was true. I beseech you, hear this again more clearly, and remember it: for I know that some understand, while others are yet enquiring perhaps what I meant.
There is no article of the Christian faith which has encountered such contradiction as that of the resurrection of the flesh. Finally, He who was born for a sign that should be spoken against, resumed His own flesh after death to meet the caviller; and He who could have so completely cured His wounds that their scars would have entirely vanished, retained those scars in His body, that He might cure the wounds of doubt in the heart. Indeed nothing has been attacked with the same pertinacious, contentious contradiction, in the Christian faith, as the resurrection of the flesh.
On the immortality of the soul many Gentile philosophers have disputed at great length, and in many books they have left it written that the soul is immortal: when they come to the resurrection of the flesh, they doubt not indeed, but they most openly deny it, declaring it to be absolutely impossible that this earthly flesh can ascend to Heaven. Thus that moon shall be perfect for evermore, and shall be the faithful witness in heaven against all gain-sayers.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)