Noah condemns the world by his faith in God’s Word. God tells Noah to build an ark, to gather two of every kind of fauna, to put his family into the ark, and to wait while the world drowns via non-stop rain for forty days and forty nights. When Noah obeys God, he condemns the world — the world which does not believe and obey. “The waters surge upon the earth 150 days.” (Genesis 7:24) And, “[God] wipes out every living thing that is on the surface of the ground, from mankind to livestock, to creatures that crawl, to the birds of the sky, and they are wiped off the face of the earth. Only Noah is left, and those that are with him in the ark.” (Genesis 7:23) For over ten months, Noah waits in the ark for God to release him and those with him. Forty days after the tops of the mountains are finally visible, Noah sends out a dove who returns. The second dove he sends out returns with an olive leaf; the third dove does not return at all. Noah waits a few months longer before God tells him to exit the ark with those saved through Noah’s obedience to God’s Word.
The world drowns in God’s rain; and by his faith, Noah condemns the world.
I’m not completely sure I understand why it is that the faith Noah has condemns the world except that his faith leads him to obey God in spite of the world’s derision. That Noah does not stand on a pedestal and shout, ‘repent for the end of the world is at hand!’ is revealing. Rather than striving to save the world from its destruction, Noah strives to do God’s will, continuing to build the ark in preparation for the flood he has been told is coming upon the whole world. Noah regards God as more important than his neighbors and friends, building the ark even as the world goes about its business of ignoring God.
By his faith, Noah saves himself and his family.