Musar על עירובין 36:13

Noach then was righteous in terms of his generation since he responded to inspiration from "above." G–d "encouraged" Noach during the one hundred and twenty years prior to the deluge. He sent him on a mission to warn his contemporaries to repent of their wicked ways. The Torah however, records only מקצת שבחו בפניו, וכלו שלא בפניו. The usual meaning of this concept is that one does not reveal all of a person's merits while he is alive, whereas when eulogizing such a person one must reveal all his merits. In this instance the meaning of שלא בפינו is that Noach did not initiate his role as the conscience of mankind, but he was prompted to do so by G–d.