Reb Menachem Nochum, the oldest son of the Mitteler Rebbe, was born around the year 5547 (1787) and resided in Lubavitch. Later on, he moved to Niezhin, making frequent extended visits to the kever of his grandfather the Alter Rebbe in Haditch. He passed away around eighty-years-old, and is buried in Niezhin.
During the time of the Alter Rebbe, a new fashion in Russia dictated that jackets should henceforth have collars. When his grandson Reb Nochum, son of the Mitteler Rebbe, was preparing for his chassuna, the Alter Rebbe called for him and asked him about his silk kapota: would it be made in the traditional way, or would it conform to the new fashion? "It'll have a collar, of course," Reb Nochum replied.
The Alter Rebbe requested that he have it made without one, but Reb Nochum, then still a young bochur, argued, "Everyone else will have one, and I'll be embarrassed." The Alter Rebbe then promised him that if he wore a kapota without a collar, he would be together with his grandfather in Gan Eden. He then asked Reb Nochum that when his kapota was ready, he should come to him dressed in it. Reb Nochum asked if he must do it wholeheartly or kabolas ol would be sufficient. The Alter Rebbe replied, "Of course it must be truthfully, and with the truth of the 'yechida.'" Reb Nochum was silent and nothing more was said.
Before the chassuna, the young man entered the Alter Rebbe's room, dressed in his new kapota... which had a collar. The Alter Rebbe then tore off a small piece of fur from the inside of the coat and promised him long life for that. Years later Reb Nochum commented, "I was young and didn't appreciate how great was the promise I had been given." To correct this incident, Reb Nochum would spend much time in Haditch by the Ohel of the Alter Rebbe.
The Rebbe explained that at that time and place, the challenge of fashions was extremely difficult. Had the Alter Rebbe been successful, that challenge would have been removed for generations to come. And that explains why he offered his grandson such a rich reward.
(לקוטי דיבורים ח"א עמוד 29, רשימו"ד חדש ע' 97, תו"מ חל"ה ע' 278)
