2 For so, as we may understand from the words of the Lord Himself, did He call back from His discipleship a certain proud man, who of his own accord was desirous to go with Him. “Lord, I will follow You wherever You go.” And the Lord seeing in his heart what was invisible, said, “Foxes have holes, and the birds of the air have nests, but the Son of Man has not where to lay His Head.” That is, in you, guile like the fox does dwell, and pride as the birds of heaven.
But the Son of Man simple as opposed to guile, lowly as opposed to pride, has not where to lay His Head; and this very laying, not the raising up of the head, teaches humility. Therefore does He call back this one who was desirous to go, and another who refused He draws onward. For in the same place He says to a certain man, “Follow Me.” And he said, “I will follow You, Lord, but let me first go and bury my father.” His excuse was indeed a dutiful one: and therefore was he the more worthy to have his excuse removed, and his calling confirmed.
What he wished to do was an act of dutifulness; but the Master taught him what he ought to prefer. For He wished him to be a preacher of the living word, to make others live. But there were others by whom that first necessary office might be fulfilled. “Let the dead,” He says, “bury their dead.” When unbelievers bury a dead body, the dead bury the dead. The body of the one has lost its soul, the soul of the others has lost God. For as the soul is the life of the body; so is God the life of the soul. As the body expires when it loses the soul, so does the soul expire when it loses God. The loss of God is the death of the soul: the loss of the soul the death of the body. The death of the body is necessary; the death of the soul voluntary.
Source: Sermons on Selected Lessons of the New Testament (New Advent)