The phrase until the day breathes
could refer to the end of the day (its last breath) or the start of the day (its first breath). In the same way, the shadows may flee as the sun goes down or when the sun comes up and rises higher and higher in the sky.1 The reference could therefore be to either the end of the day, or the end of the night. Since the young woman is using the phrase to speak of that much-anticipated day when their relationship will finally be consummated on their wedding night, it is more likely that she is referring to the break of day, or morning, as she anticipates a whole night of love.
This phrase is used in a similar way in Song of Solomon 4:5–6 where the description of the woman’s breasts, which are like twin fawns or a gazelle browsing the lilies, is also followed by a reference to the day breaking
and the shadows fleeing
and then by a statement of the man’s intention of going to the mountain of myrrh and to the hill of incense
(Song of Solomon 4:6).2 The context here is also one of sexual intimacy.
17 Until the day breathes and the shadows flee, turn, my beloved, be like a gazelle or a young stag on cleft mountains.