When a person told the Rebbe at ‘Dollars’ that he once attended a Tomchei Temimim yeshiva, the Rebbe clarified that it wasn’t something that he could get away from.
In a sicha on the seder night 5713 (1963), the Rebbe stated, “Once one has a connection to the Rebbe, even if it is minimal – that only occasionally he learns a maamar, or supports the Rebbe’s endeavors – his fate has been sealed. He will forever have a relationship with the Rebbe!”
On the 15th of Elul 5751 (1991), the day the original Tomchei Temimim yeshiva was established in Lubavitch in 5657 (1897), a man approached the Rebbe on the dollars line.
Although he was not a chossid, he said to the Rebbe that in his youth he had once studied at a Tomchei Temimim yeshiva.
The Rebbe corrected his wording, “If you were once a tomim, you remain a tomim for life. You don’t have a choice.”
(Zorea Tzedakos Matzmiach Yeshuos, Page 136)
From The Weekly Farbrengen by Merkaz Anash