The Rebbe blesses him on reaching 81 years with long life, health, and continued strength in tzedakah, Torah study, Tehillim, and communal learning. He explains the deeper meaning of the “third day”—a harmony of body and soul in serving Hashem—encouraging him to live with this higher service, especially in later years, with joy and peace.
https://www.torahrecordings.com/rebbe/004_igros_kodesh/elul/1174