In Genesis, Noah took seven pairs of every clean kind of animal aboard the Ark.
Genesis 7:2 tells Noah to take seven pairs, male and female, of clean animals, while specifying one pair of animals that were not clean. Genesis 7:3 separately says to take seven pairs of birds. This distinction is why the simplified phrase “two of every kind” does not fully represent the instructions in the final flood narrative.
The clean-animal distinction is connected with sacrifice and food in the story. After leaving the Ark, Noah builds an altar and offers burnt offerings from every clean animal and every clean bird. Genesis 8:20 therefore helps explain why the narrative gives clean animals a different number from other animals.