In Genesis, Noah was told to take seven pairs of clean animals into the Ark.
Genesis 7:2 distinguishes between clean and unclean animals. It instructs Noah to take seven pairs of the clean animals, meaning male and female, while the unclean animals are represented by one pair. Genesis 7:3 gives a similar instruction for birds, using language about seven pairs or sevens in many translations.
This detail is often simplified in popular retellings into the idea that every animal entered as only one pair. That is not the distinction made by the Genesis passage. The clean-animal instruction is also connected with the sacrifices Noah makes after leaving the Ark.
Translation and interpretation can affect whether the wording is rendered “seven pairs” or “seven of each,” but the familiar English answer to the clean-animal question is seven pairs.