Mechila Before Yom Kippur

A מבהיל-דיגא Sfas Emes: In the eighth perek of Yoma he writes that before Yom Kippur one must ask mechila from his friend who is angry with him EVEN IF THE ANGER IS NOT JUSTIFIED. So if my friend is annoyed with me for not giving him a loan of ten thousand dollars when he needed it, when the fact was that I don't have ten thousand dollars and he has no right to be angry with me - I still have to ask him for mechila before Yom Kippur. The rest of the year you don't have to ask but Yom Kippur is different.

The Rebbe mentioned this in his shiur tonight and said מצוה לפרסם.