-- Be less willing to kill their enemies the worse the enemy is

Now might I do it pat. Now he is praying.
And now I’ll do ’t. And so he goes to heaven.
And so am I revenged.—That would be scanned.
A villain kills my father, and, for that,
I, his sole son, do this same villain send
To heaven.
Oh, this is hire and salary, not revenge.
He took my father grossly, full of bread,
With all his crimes broad blown, as flush as May.
And how his audit stands who knows save heaven?
But in our circumstance and course of thought
'Tis heavy with him. And am I then revenged
To take him in the purging of his soul
When he is fit and seasoned for his passage?
No.
Up, sword, and know thou a more horrid hent.
When he is drunk asleep, or in his rage,
Or in th' incestuous pleasure of his bed,
At game a-swearing, or about some act
That has no relish of salvation in ’t—
Then trip him, that his heels may kick at heaven,
And that his soul may be as damned and black
As hell, whereto it goes. My mother stays
This physic but prolongs thy sickly days.

-- Hamlet, Act 3, scene 3.