And Noah builded an altar — Hitherto he had done nothing without particular instructions and commands from God but altars and sacrifices being already of Divine institution, he did not stay for a particular command thus to express his thankfulness. And he offered on the altar, of every clean beast and of every clean fowl — One, the odd seventh that we read of, Genesis 7:2-3.
Related Commentaries of Genesis 8:20
Genesis 8:20
20 And Noah builded an altar unto the LORD; and took of every clean beast, and of every clean fowl, and offered burnt offerings on the altar.