This 13th century chant serves as the Sequence in the traditional Roman Rite Requiem, or Mass for the Dead. A complete translation of the text may be found here: https://archive.ccwatershed.org/.../21/03/23/22-31-07_0.pdf
This chant has accompanied countless Requiems through the centuries. We pray it accompanied the Holy Father as he was laid to rest. Eternal rest grant unto Pope Benedict XVI O Lord, and may perpetual light shine upon him. May he rest in peace. Amen.