Psalms 103:5

However, rightly so, a man has not many, but two feet; for four feet belong to wild animals and beasts, and two to birds. Therefore, a man is like a bird, who seeks lofty things with his sight and flies with a certain stroke of the senses' keenness. And therefore it is said about him: Your youth will be renewed like the eagle's; because he is closer to heavenly things and higher than eagles, who can say: But our conversation is in heaven.

And that the writer was speaking of baptism is evident from the very words in which it is stated that it is impossible to renew to repentance those who were fallen, inasmuch as we are renewed by means of the laver of baptism, whereby we are born again, as Paul says: "For we are buried with him through baptism into death, that, as Christ rose from the dead through the glory of the Father, so we, too, should walk in newness of life." And in another place: "Be renewed in the spirit of your mind, and put on the new person that is created after God." And elsewhere again: "Your youth shall be renewed like the eagle," because the phoenix after death is born again from its ashes, as we being dead in sin are through the sacrament of baptism born again to God and created anew. So, then, here as elsewhere, he teaches one baptism. "One faith," he says, "one baptism."

But let us speak of death as common to all people. Why should we be afraid of it, when it generally does not harm the soul? For it is written, "Do not be afraid of those who kill the body but cannot kill the soul." Now through death the soul is freed, while it separates itself from the dwelling place of the body and divests itself of the wrappings of disquiet. And so let us too, while we are in the body, following the way of death, raise up our bodies from this fleshly couch and arise from the tomb, as it were. Let us withdraw from the bond of the body and leave all things whatsoever that are of earth, so that when the adversary comes he may find nothing of his in us. Let us strive for the eternal and fly up to the divine on the wings of love and the oars of charity. Let us rise up from here, that is, from the things of the age and those of the world. For the Lord has said, "Arise, let us go from here," teaching that each one should arise from the earth, raise up his soul that lies on the ground, lift it to the things that are above and call forth his eagle, the eagle of whom it is said, "Your youth will be renewed like the eagle's."