LYRICS:

Os iusti meditabitur sapientiam
et lingua eius loquetur iudicium
beatus vir qui suffert tentationem
quoniam [bad word] probatus fuerit
accipiet coronam vitae

Kyrie, ignis divine, eleison
Oh quam sancta
quam serena
quam benigna
quam amoena
Oh castitatis lilium

TRANSLATION
( thanks to Lunaange ):

The mouth of the just shall meditate wisdom
And his tongue shall speak judgement
Blessed the man who resists temptation
For when proved he shall receive the crown of life
Lord, Divine Fire, have mercy
O how holy, how serene
How benevolent, [bad word] 
O Lily of Chastity.