On 25 Elul 5724, (1964) the Rebbe returned a letter to Rabbi Dovid Okunov in which he signed off as M. Zeide. The Rebbe did  so as not to endanger Reb Dovid. Reb Dovid addressed the Rebbe as "Zeide" because the KGB, the Communist secret police, was aware of Rabbi Schneerson in America. Any affiliation with religion was strictly forbidden and interception and censoring of mail was routine. In his letter, the Rebbe alluded to Reb Dovid leaving Russia. He wrote to him in Russian:

"To my dear grandson Dovid,

Shalom.

I was very happy to receive regards from you. I was also very pleased to be informed that you have received an 'invitation' to live together with your relatives, and I wish you much happiness. May Hashem Yisborach grant that all your wishes be fulfilled without any difficulties in the most complete measure. And may we all stand together in time for the Chagim.

With best wishes to all of you for the New Year,

M. Zeide"