By the night when it overshadows.
By the night as it covers
By the night, when it envelops
By the night when it draws a veil
And/by the night when/if it covers/darkens
Hereby God swears by the night as it covers the earth
By oath of the night when it cover
By the night when it covers up
By the night when it covers up (and conceals everything in its darkness)
I call to witness the night when it spreads (its) veil
By the night as it envelops