To And Fro - Genesis 8:6-7

Genesis 8:6-7 ESV 

At the end of forty days Noah opened the window of the ark that he had made

and sent forth a raven. It went to and fro until the waters were dried up from the earth.

Forty days is a re-occurring number appearing frequently in Scripture that represents a time of trial, such as the time Moses spent on the mountain, the Israelites wandering in the desert, or the temptations of Jesus during His time in the wilderness. 

Noah opens the only window which lets in the light after the rain and sends forth a raven. The raven goes "to and fro" on the earth, as Satan did in Job. This is the first of two birds released in this new world. One may be reminded that the earth was dark and formless before the appearance of light. 

It is God Who releases the birds. 

Satan will have dominion over the earth until the waters are dried from the earth and the sea is no more. The beasts of Satan rise from the waters of humanity to oppose God, but the dominion of Satan will disappear.