One Sunday morning in 1991, Rabbi Peretz Hecht, my father Rabbi Chaim Meir Bukiet, and I, waited together in the famous line that led to where the Rebbe, of righteous memory, would distribute dollars to be given to charity.
Rabbi Hecht approached the Rebbe first. The Rebbe gave him a dollar, and then handed him another dollar saying, "This [dollar] is for your mother." Rabbi Hecht froze; his mother had passed away many years ago.
The Rebbe, noting Rabbi Hecht's confusion, repeated, "For your mother."
Rabbi Hecht stared at the Rebbe, unable to utter a word. The Rebbe asked with a smile, "You know that you have a mother?!"
Rabbi Hecht bent over and whispered to the Rebbe's aide, Rabbi Leibel Groner, that his mother had passed away many years ago. Rabbi Groner repeated this information to the Rebbe. The Rebbe immediately responded, "And so what?"
Rabbi Hecht took the dollar for his deceased mother and left, very puzzled and befuddled.
Immediately after exiting the building, Rabbi Hecht began to cry out, "Oy vay! Today is my mother's birthday!"
The Rebbe gave him a dollar for charity to be given in his mother's merit on her birthday.

In honor of my Zaidy Peretz Hecht's passing today. I saw the clip of this dollars and I guess the story teller remembers it but not precise.The story was that my Zaidy went by the Rebbe for dollars and the Rebbe gave another dollar and said "Dos Iz Far De mameh" -This is for the mother. Zaidy was puzzled as his mother passed away years before but took the dollar with a smile and went on. Rabbi Leibel Groner asked the Rebbe that Reb Peretz's mother passed away long ago? The Rebbe called Zaidy back and told him " Dos Iz Lzecher Haneshama"- This is in memory of the soul that passed on reffering to his mother (The Rebbe called Zaidy back to explain what the Rebbe meant the first time). Possibly the last part of the story is true as the clip does not show it-He realized that it was also his mothers Birthday when he left the Rebbe and understood why the Rebbe gave him an extra dollar in her memory for charity. May Zaidy Peretz be with us again with Moshiach Now!
This story took place on the evening of 10 Nissan, 5748 - March 28, 1988 at the Rebbe's home on President street.
Here is the video