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. 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. 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. 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.
Here, God gives Noah more specific instructions. Creatures that were considered clean, which were worthy of sacrifice to God (see 8:20), were commanded to be permitted in by sevens, rather than the twos that the common animals came as. Clean beasts were understood as different from other animals. Perhaps, could the difference between clean and unclean have to do with a genetic code that was corrupted by what was happening before the Flood? It is no coincidence that with Christ’s resurrection all animals were made clean.
Acts 10:9 ¶ On the morrow, as they went on their journey, and drew nigh unto the city, Peter went up upon the housetop to pray about the sixth hour: 10 And he became very hungry, and would have eaten: but while they made ready, he fell into a trance, 11 And saw heaven opened, and a certain vessel descending unto him, as it had been a great sheet knit at the four corners, and let down to the earth: 12 Wherein were all manner of fourfooted beasts of the earth, and wild beasts, and creeping things, and fowls of the air. 13 And there came a voice to him, Rise, Peter; kill, and eat. 14 But Peter said, Not so, Lord; for I have never eaten any thing that is common or unclean. 15 And the voice spake unto him again the second time, What God hath cleansed, that call not thou common.
In any case, it is clear that prior to the Law given to Moses there was an understanding of God’s standard of clean and unclean animals. Clean animals were brought into the ark by sevens and unclean by twos. The literal reality is far different than that in the popular imagination of all creatures being brought in twos. Still, these were probably not a huge variety of animals, based on the information given later in the Law. Birds are included in the groups of sevens brought in so what we would today consider in the taxonomic classification of “family” had its bird representatives.
Noah has a week before it starts to rain, something that this world may have not seen previous, based on the statement of how the earth was set before the Flood.
Genesis 2:6 But there went up a mist from the earth, and watered the whole face of the ground.
Notice that every living substance in verse 4 is conditioned by what God said previously and the whole context must be taken into account in order to get at what is really being said. Context and cross-referencing are essential to interpreting the Bible truthfully and faithfully if you do not have an agenda other than explaining what has been left for us, rather than some social or political purpose of manipulation and control.
We will soon see that more was involved than just rain.