Genesis 6:20

of fowls after their kind, and of cattle after their kind, of every creeping thing of the earth after his kind, two of every sort shall come unto thee to keep them alive. This was God's provision against the total extermination of the animals with the breath of life. A pair of every kind, at the instigation of God, came to the ark and was admitted by Noah. This was true of the larger mammals as well as of the birds and reptiles: they all were to be kept alive in the midst of the general destruction.