Study
18 And to rule over the day and over the night, and to divide the light from the darkness: and God saw that it was good.
'To open,' as in Revelation 9, signifies communication and conjunction.
(References: Apocalypse Explained 537)
34 The lamp of the body is the eye. Therefore when your eye is good, your whole body is also full of light; but when it is evil, your body also is full of darkness.