Genesis 6:19

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.

Genesis 7:2

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.

In Genesis chapter 6, God tells Noah to bring 2 of every sort of animal into the ark. In chapter 7, God tells Noah to bring 7 of every clean beast into the ark.

Notice that Genesis 7:2 reiterates the command given in Genesis 6:19 to bring two of every sort of animal. However, Noah is now told to bring 5 more pairs of the clean animals. And, while it is true that if 7 pairs are brought on the ark, then it is also true that 2 pairs are brought on the ark, I don't think we even need to get that pedantic. Genesis 6:19 was a broad command that would apply to virtually all animals. Genesis 7:2 is simply giving more detail, and includes an additional command in regard to bringing extra clean pairs.