This photo represents Macbeth stabbing Duncan in the back. Duncan trusted Macbeth and considered him a friend. In Macbeth's need to sit on the throne he betrayed his king and friend by murdering him well he was asleep.
Shakespeare The Taming of the Shrew: "My tongue will tell the anger of my heart, or else my heart concealing it will break." - La mia lingua dirà la collera del mio cuore, o altrimenti il mio cuore celandola si spezzerà.