seven days. The number of spiritual perfection (App-10). All the Flood dates are Sabbaths except one (Genesis 8:5).
forty. The number of probation (App-10).
destroy. wipe out, blot out.
earth. Hebrew. 'adamah = ground.
Related Commentaries of Genesis 7:4
Genesis 7:4
4 For yet seven days, and I will cause it to rain upon the earth forty days and forty nights; and every living substance that I have made will I destroyc from off the face of the earth.