Josquin's Ave Maria is one of my favorites and I was blessed enough to sing it in college. I especially like the end: O Mater Dei, memento mei. Amen! (Oh, Mother of God, remember me! Amen!) It is written to be sung with such hushed emotion!
"Slavery ended in medieval Europe only because the church extended its sacraments to all slaves and then managed to impose a ban on the enslavement of Christians (and of Jews). Within the context of medieval Europe, that prohibition was effectively a rule of universal abolition. "— Rodney Stark