Genesis 6:17-18, 22

Behold, I, even I am bringing the flood of water upon the earth, to destroy all flesh in which is the breath of life, from under heaven; everything that is on the earth shall perish. But I will establish My covenant with you; and you shall enter the ark—you and your sons and your wife, and your sons’ wives with you.

Thus Noah did; according to all that God had commanded him, so he did.