This meditation is from a sermon by St. Peter Chrysologus (ca. 400-450):
It is by dying that your shepherd proves his love for you. When danger threatens his sheep and he sees himself unable to protect them, he chooses to die rather than to see calamity overtake his flock. What am I saying? Could Life himself die unless he chose to? Could anyone take life from its author against his will? He himself declared: “I have power to lay down my life, and I have power to take it up again; no one takes it from me.” To die, therefore, was his own choice; immortal though he was, he allowed himself to be put to death.
Lamentation , Giotto (1304-1306)
By allowing himself to be taken captive, he overpowered his opponent; by submitting he overcame him; by his own execution he penalized his enemy, and by dying he opened the door to the conquest of death for his whole flock. And so the Good Shepherd lost none of his sheep when he laid down his life for them; he did not desert them, but kept them safe; he did not abandon them but called them to follow him, leading them by the way of death through the lowlands of this passing world to the pastures of life.