In Parshat Lech Lecha, among the blessings that Avraham was to receive for leaving all that he had was the blessing that he himself should be a blessing (12:2). How does one become a blessing? Furthermore, Rashi comments that G-d promised Avraham that although he would be identified with Yitzchak and Yakov, any such blessings would end with Avraham's name at its conclusion. If the sages are correct that Yitzchak and Yakov reached higher levels than Avraham, what made him so special that any blessing would end with him?
Rav Moshe Feinstein explains that Avraham merited greater distinction because he was the first to establish faith in Hashem (G-d). Although those after him reached greater heights, Avraham's accomplishments were more worthy. Maybe this can explain how Avraham himself became the blessing: Taking initiative and starting something you believe is important for society is a blessing on its own, because it lays the framework for others to build on it! G-d promised Avraham, and in turn promised us, that, if we become leaders and initiators, our initial efforts will never be forgotten and we will always be remembered as a blessing!