St. Liborius was born in the fourth century of a Gaulish family and left everything to consecrate himself to the service of the altar. He became bishop of Le Mans and after a life devoted to preaching, prayer and austerities he died in AD 397.
Statuit ei Dominus testamentum pacis, et principem fecit eum: ut sit illi sacerdotii dignitas in aeternum. * Memento, Domine, David, et omnis mansuetudinis ejus.
The Lord made to him a covenant of peace, and made him a prince: that the dignity of the priesthood should be to him for ever. * O Lord, remember David: and all his meekness.
(Ecclesiasticus 45:30 and Psalm 131:1 from the Introit of Mass)
Be mindful of our weakness, O almighty God, and since the burden of our deeds is grievous to us, grant that the glorious intercession of blessed Liborius Thy martyr and bishop may protect us.
From the Catholic Encyclopaedia: http://www.newadvent.org/cathen/09143b.htm