From J, but touched by the redactor in Genesis 7:3 a. J's account of the command to build the ark and its fulfilment has been omitted in favour of P's. J recognises the distinction between clean and unclean, which P regards as introduced by Moses; the same is true of the sacrificial system. A week is allowed for bringing in the animals. Whether seven or seven pairs of the clean animals were taken in is disputed; probably the latter. Unless Genesis 7:3 a is struck out as a gloss, we must follow the LXX, which gives the same directions for birds as Genesis 7:2 gives for animals.
Related Commentaries of Genesis 7:1
Genesis 7:1-5
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,a 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,b 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 destroyc from off the face of the earth.
5 And Noah did according unto all that the LORD commanded him.