Ceramic teacup by Chris Warren.
Back in the days when Ethan and I studied Isshin-Ryu with Sensei Steve Buschman, we learned the parable of Nan-in and the teacup. (I heard it again at some point during my hashpa'ah training.) Here's how it goes:
A zen student came to the zen master Nan-in seeking wisdom, and they sat down to tea.
Nan-in poured tea into the student's cup. And then kept pouring. And the tea overflowed. Eventually the student could not contain himself, and exclaimed, "Can't you see that the cup is already full?"
"Just so," said the Zen master, "You are already full of opinions and certainties. I can't teach you until you first empty your cup."
In spiritual direction a few days ago, I re-learned that the Baal Shem Tov, the founder of Hasidism, taught that it is necessary to "give over" Torah -- to teach Torah to others -- in order to open oneself up to receive more Torah. When one teaches Torah, that act stimulates the flow of more Torah from on high.
(This is what kabbalah calls itaruta di'l'tata -- Aramaic for "arousal from below." When we give over Torah, when we give over blessings, our action "arouses" the divine will, and God pours more Torah and more blessing into the world.)
In order to receive more Torah, one has to give over the Torah one has already received. In order to receive the wisdom of zen, one must first empty one's teacup: relinquish preconceptions in order to receive that which is new.
They're not quite the same teaching. Nan-in was interested in clearing the mind of preconceived notions and assumptions in order to make space for new learning, new insights, new understandings. The BeShT was interested in the act of teaching, of giving-over Torah to students, as a mystical stimulus which would open the divine spigot and cause more Torah to flow into creation.
But I love the way that, in each of these paradigms, it's important to notice when one's teacup is full, and to share what one has with others, in order to make room for more. If one hoards blessings, then new blessings can't flow. If one maintains a full teacup, then there's nowhere for new tea to go. The only way to receive more is to give what you have.