This is among four Marian antiphons, with subsequent versicles and prayers, typically said or sung after night time prayer, immediately prior to planning to sleep. It is claimed through the conclude of Eastertide till the start of Introduction. This arrangement has a bridge that intersperses lines from another Marian hymn, https://vita-pro-nobis76431.shotblogs.com/the-smart-trick-of-vita-pro-nobis-that-nobody-is-discussing-45127325