Siman 212

(28.) After Shavuos in Uman, when he entered the house of Rabbi Yosef Shmuel, he began to say a Torah and did not finish it. And I was not present then, and I heard that he mentioned there that regarding the false famous leaders who have a name and renown in the world, it is said: "And you shall not mention the names of other gods." He also mentioned that there are true tzaddikim whose name has been concealed — that is, who do not have the name and renown that is due to them — and this is the aspect of [Exodus 3:15]: <span class="verse">"This is My name forever"</span> — [the word l'olam "forever" being read as l'alem, "to conceal"]. And I did not merit to hear this matter at all from his holy mouth.