6:19 And of every living thing of all flesh, two of every sort shalt thou bring into the ark, to keep them alive with thee; they shall be male and female.
6:20 Of fowls after their kind, and of cattle after their kind, of every creeping thing of the earth after his kind, two of every sort shall come unto thee, to keep them alive.
6:21 And take thou unto thee of all food that is eaten, and thou shalt gather it to thee; and it shall be for food for thee, and for them.
Then JUST SEVEN DAYS BEFORE THE FLOOD, God decides that he didn’t really mean two of each kind; he meant SEVEN of each clean kind. It is unlikely that Noah even knew what constituted a clean animal since that wasn’t determined until long after the boat floated.
7:1 And the LORD said unto Noah, Come thou and all thy house into the ark; for thee have I seen righteous before me in this generation.
7:2 Of every clean beast thou shalt take to thee by sevens, the male and his female: and of beasts that are not clean by two, the male and his female.
7:3 Of fowls also of the air by sevens, the male and the female; to keep seed alive upon the face of all the earth
7.4 .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 destroy from off the face of the earth.
Summarizing for those of you who are shocked into disbelief, just SEVEN days left before the flood, God informs six hundred year old Noah that SEVEN times as many guests as Noah expected (thankfully only the clean ones however) will be coming to the party. Thus in seven days, Noah must change the whole configuration of the ship, gather enough food to feed seven times more guests than he expected and then go out and round up the guests – for this time God does not say that they will just “show up” at the boat.