In Genesis, Noah took one pair of each kind of unclean animal onto the Ark.
Genesis 6:19–20 gives the general instruction to bring two of every kind, male and female. Genesis 7:2–3 then distinguishes between animals considered clean and unclean, telling Noah to take seven pairs of clean animals but one pair of unclean animals.
The wording can be difficult because translations differ over whether “seven” means seven pairs or seven individual animals. The contrast involving unclean animals is clearer: one male and one female, or one pair.
The distinction also connects the Flood story with later biblical dietary and sacrificial categories. Genesis presents the clean animals as more numerous, partly because they could be used for sacrifice after Noah left the Ark.