Caravaggio
The Martyrdom of St. Matthew

The Golden Legend says that St. Matthew was assassinated while saying mass.  Thus we see an altar (marked by a Greek cross on its front) in the background of the painting. 

As in his "Calling of St. Matthew" on the opposite wall, Caravaggio shows the moment of near refusal that precedes acceptance of God's will.  An angel leans down from the top of the painting to hand the saint the palm of martyrdom that we know he will accept in the next moment, but right now he is furiously resisting his assassin.

More of Saint Matthew