Francisco Guerrero (1528–1599)

Original Text 
 
Duo seraphim clamabant,
alter ad [bad word] 
Sanctus, Sanctus, Sanctus,
Dominus Deus Sabaoth.
Plena est omnis terra gloria ejus.
Tres sunt qui testimonium dant 
in coelo.
Pater, Verbum, et Spiritus Sanctus
et hic tres unum sunt.
Gloria Patri et filio,
et Spiritui sancto,
Plena est omnis terra gloria ejus. Amen. 

English Translation

The two Seraphim proclaimed
one to the other:
Holy, Holy, Holy,
Lord God of Hosts.
The whole earth is full of His glory.
There are three who give testimony
in heaven:
the Father, the Word, and the Holy Spirit;
and these three are one.
Glory be to God the Father and Son,
and the Holy Spirit:
the whole earth is full of His glory. Amen.