When Cain and Abel first offered their sacrifices,
God considered not so much the gifts
as the spirit of the giver;
God was pleased with Abel's offering
because He was pleased with Abel's spirit.
Thus Abel the just man, the peacemaker,
in his blameless sacrifice taught us
that when they offer their gift at the altar,
they should approach as he did,
in the fear of God and simplicity of heart,
ruled by justice and perfect harmony.
Since this was the character of Abel's offering,
it was only right that he himself should afterward become a sacrifice.
As martyrdom's first witness,
and possessing the Lord's qualities of justice and peace,
he foreshadowed the Lord's passion
in the glory of his own death.
---from a treatise on the Lord's Prayer by St. Cyprian of Carthage, bishop and martyr