Why does Antony call Caesar a bleeding piece of earth in Shakespeare's Julius Caesar?
Shakespeare seems to be alluding to the story in Genesis that God created man out of the dust and breathed life into him. Antony could not see his friend's body as the living person he knew, and the analogy with something made out of dirt or clay may have occurred to him just as it did to the author of Genesis. There are two references to man being made out of dirt or dust in Genesis.
And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul (Chapter 2, Verse 7).
In the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou art, and unto dust shalt thou return (Chapter 3, Verse 19).
Although Antony sees Caesar's body as something that will soon turn to dust, he also sees Caesar's body is still bleeding from its wounds. It is not Caesar, but something that the soul of Caesar has left behind. Caesar himself is immortal, in Antony's conception, and will return to take his revenge on those who murdered him. Antony does not want to address the corpse as Caesar because that would negate the idea that Caesar's spirit has gone elsewhere and will return.
It is significant that Antony addresses this soliloquy to the corpse of Caesar. Soon, he will be carrying it before the assembled commoners to make his forthcoming funeral address and he will be using Caesar's mutilated body to incite a mutiny.
O, pardon me, thou bleeding piece of earth,
That I am meek and gentle with these butchers!
Thou art the ruins of the noblest man
That ever lived in the tide of times.
Woe to the hand that shed this costly blood!