1 “Like sheep laid in hell, death is their shepherd”. Whose? Of those whose way is a stumbling-block to themselves. Whose? Of those who mind only things present, while they think not of things future: of those who think not of any life, but of that which must be called death. Not without cause, then, like sheep in hell, have they death to their shepherd. What means, “they have death to their shepherd”? For is death either some thing or some power? Yea, death is either the separation of the soul from the body, or a separation of the soul from God, and that indeed which men fear is the separation of the soul from the body: but the real death, which men do not fear, is the separation of the soul from God.
And ofttimes when men fear that which does separate the soul from the body, they fall into that wherein the soul is separated from God. This then is death. But how is “death their shepherd”? If Christ is life, the devil is death. But we read in many places in Scripture, how that Christ is life. But the devil is death, not because he is himself death, but because through him is death. For whether that (death) wherein Adam fell was given man to drink by the persuasion of him: or whether that wherein the soul is separated from the body, still they have him for the author thereof, who first falling through pride envied him who stood, and overthrew him who stood with an invisible death, in order that he might have to pay the visible death.
They who belong to him have death to their shepherd: but we who think of future immortality, and not without reason do wear the sign of the Cross of Christ on the forehead, have no shepherd but life. Of unbelievers death is the shepherd, of believers life is the shepherd. If then in hell are the sheep, whose shepherd is death, in heaven are the sheep, whose shepherd is life. What then? Are we now in heaven? In heaven we are by faith. For if not in heaven, where is the “Lift up your heart”?
If not in heaven, whence with the Apostle Paul, “For our conversation is in heaven”? In body we walk on earth, in heart we dwell in heaven. We dwell there, if there we send anything which holds us there. For no one dwells in heart, save where thought is: but there his thought is, where his treasure is. He has treasured on earth, his heart does not withdraw from earth: he has treasured in heaven, his heart from heaven does not come down: for the Lord says plainly, “Where your treasure is, there will your heart be also.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)