Tosefta su Levitico 24:78

The family of the house of Tzarifah was over the Jordan and Ben Tzion kicked it out by force. And there was another [family] there and Ben Tzion brought it close by force. The Sages did not want to reveal them, but they transmit to their children and to their students once in seven [years]. [Families] like these Eliyahu comes to deem unclean and clean, to send away or bring near. Rabbi says, to draw near but not to send away. Rabbi Yehuda says, the matters are reversed. Rabbi Hananya ben Ado says, indeed it says, “There came out among the Israelites a man whose mother was Israelite and whose father was Egyptian, and the half-Israelite and another Israelite fought” (Lev 24:10). These matters [produce] a qal v’homer: just as Moses our teacher did not want to reveal the mamzers until they revealed themselves, Elijah—Moses’s student—all the more so would not reveal until they revealed themselves. The one has students, they call him rabbi. When his students were forgotten, they called him rabban. When both of these are forgotten, they call him by his name.