A teaching from the life of Rebbe Zusya of Hanipol, Menorat Zahav, Parshat Bamidbar
These are the descendants of Aaron and Moses… וְאֵלֶּה תּוֹלְדֹת אַהֲרֹן וּמֹשֶׁה Numbers 3:1
Rashi points out that the Torah only mentions the descendants of Aaron, and explains that they are counted as Moses’ descendants because he taught them Torah, and whoever teaches his fellow’s son Torah is counted as his father.
Rebbe Israel of Rizhin told how, when Rebbe Zusya was at the house of his master, Rabbi Dov Ber the Maggid of Mezeritch, and the Maggid began a teaching, saying, “And God said to Moses…,” Rebbe Zusya would feel the power of the Torah and begin to thrash about and overturn the table. There were other great men at the Maggid’s house, the Berditchever Rebbe and Rebbe Nahum of Chernobyl, and they would take him outside and he would stand there crying out, “And God said! And God said!” When the Maggid stopped saying Torah Rebbe Zusya too would stop, and they would bring him back inside. So Rebbe Zusya knew only the beginnings of the Maggid’s teachings, but not the rest. The Rizhiner finished, “Now I say the truth is that when the tzaddik speaks in truth and the listener listens in truth then with one word they can bring the whole world close and with one word they can purify it.”
Now we can understand the saying of the sages, “One who teaches another Torah, it is as if he gave birth to him.” For just as [the man’s part] in giving birth takes very little time, and yet the child is forever after known as his son, so one moment of Torah, if given over in truth, can give birth to a new person.