On Gim mel Tam muz, when the Rebbe was released from prison for a few hours before continuing to his exile in Kostroma, R. Zalman was admitted entry to the Rebbe. As he relates:
“On Sunday, the third of Tam muz — when the Rebbe still hadn’t come — and my brother-in-law R. Yitzchak Minkovitch and I went outside for a while, Pinya came running to us with the news that the Rebbe had already reached home. We im mediately ran there, and the Rebbe was sitting in the children’s room.
“One of the daughters entered the room and said, ‘Tateh, the yungeleit want to see you. ’
“‘Have you been learning Chassidus during this time?’ the Rebbe asked us the moment we came inside.
“‘We’ve been saying Tehillim,’ my brother-in-law answered.
“The Rebbe replied im mediately: ‘I wrote the maamarim of Shavuos until they saw me and took away the pencil. ’”
A few hours later, the Frierdiker Rebbe gave out the maamorim of Shavuos through our Rebbe, on which he noted that they had been written in prison.
As I Heard Them, Vol. 1, pp. 430-432, no. 24 Continued from the biography of R. Zalman Duchman: