St Ambrose, Bishop, Confessor and Doctor
He enriched the Divine office with sacred hymns to be chanted by the congregation. The Milanese liturgy is still known as the "Ambrosian Rite." This great bishop died in 397, during the night of Saturday in Holy Week.
In the midst of the Church the Lord opened his mouth: and He filled him with the spirit of wisdom and understanding: He clothed him with a robe of glory. * It is good to give praise to the Lord: and to sing to Thy name, O most High.
(Ecclesiasticus 15:5 and Psalm 91:2 from the Introit of Mass)
Deus, qui pópulo tuo aetérnae salútis beátum Ambrósium minístrum tribuísti: praesta, quaesumus; ut, quem Doctórem vitae habúimus in terris, intercessórem habére mereámur in coelis.
O God, who didst give unto Thy people blessed Ambrose to be a minister of eternal salvation: grant, we beseech Thee, that we may be worthy to have as an intercessor in heaven him, whom we have had as a teacher of life on earth.
Catholic Encyclopaedia: http://www.newadvent.org/cathen/01383c.htm