Cross reference
Genesis 7:17
17 And the flood was forty days upon the earth; and the waters increased, and bare up the ark, and it was lifted up above the earth.
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 thing that I have made will I destroy from off the face of the ground.
Genesis 7:12
12 And the rain was upon the earth forty days and forty nights.