The fifth of the O Antiphons.

O Oriens,
splendor lucis æternae,
et sol justitiæ:
veni, et illumina
sedentes in tenebris,
et umbra mortis.

In English:

O Dawn,
Splendor of eternal light,
And sun of justice,
Come, and illuminate
Those seated in darkness,
And in the shadow of death.