When they saw Patroklos dead
—so brave and strong, so young—
the horses of Achilles began to weep;
their immortal nature was upset deeply
by this work of death they had to look at.
They reared their heads, tossed their long manes,
beat the ground with their hooves, and mourned
Patroklos, seeing him lifeless, destroyed,
now mere flesh only, his spirit gone,
defenseless, without breath,
turned back from life to the great Nothingness.

Zeus saw the tears of those immortal horses and felt sorry.
"At the wedding of Peleus," he said,
"I should not have acted so thoughtlessly.
Better if we hadn't given you as a gift,
my unhappy horses. What business did you have down there,
among pathetic human beings, the toys of fate.
You are free of death, you will not get old,
yet ephemeral disasters torment you.
Men have caught you up in their misery."
But it was for the eternal disaster of death
that those two gallant horses shed their tears.

Constantine P. Cavafy

http://www.poemhunter.com/poem/the-horses-of-achilles-2/