This depiction of Diego Velázquez's crucifixion is accompanied by the setting of Psalm 50(51) composed by Gregorio Allegri (1582-1652) - both masterpieces of the 1630s. Allegri's setting was originally deemed so sublime, that it was only ever performed annually on Spy Wednesday and Good Friday in the Sistine Chapel. Transcribing it or performing it elsewhere was punishable by excommunication.
Miserere mei, Deus:
Have mercy on me, O God,
secundum magnam misericordiam tuam.
according to thy great mercy.
Et secundum multitudinem
And according to the multitude
of thy tender mercies
dēlē iniquitatem meam.
blot out my iniquity.
Amplius lavā me ab iniquitate mea:
Wash me yet more from my iniquity,
et a peccato meo mundā me.
and cleanse me from my sin.
Meanwhile, the faithful keep watch, preparing for the great Vigil.