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The following is the complete text, which may be used at the procession of a bishop at a solemn celebration of ordination.
Ecce sacerdos magnus, qui in diébus suis plácuit Deo: Ideo jure jurando fecit illum Dóminus crescere in plebem suam. Benedictiónem ómnium géntium dedit illi, et testaméntum suum confirmávit super caput ejus. Ideo jure jurando fecit illum Dóminus crescere in plebem suam. Gloria patri et filio et spiritui sancto...
Behold a great priest who in his days pleased God: Therefore by an oath the Lord made him to increase among his people. To him He gave the blessing of all nations, and confirmed His covenant upon his head. Therefore by an oath the Lord made him to increase among his people. Glory to the Father and to the Son and to the Holy Spirit. . .
The priest mentioned in the hymn refers to Christ, the high priest, in whose place the bishop stands.
Here a seminary rendition of Tu Es Sacerdos
Here a seminary rendition of Tu Es Sacerdos