His Father Appears in White

It is described in Zohar Chai, the sefer of Rav Yitzchok Isaac, that before his passing Rav Yitzchok Isaac appeared robed in all white and called over his son, Rav Eliezer Tzvi.

He commanded his mother to dress in her Yom Tov clothes and pearls for the occasion, for she was about to witness her son's ascension as rebbe and leader. He also told his son that from now on he should wear white on Shabbos, as one fit to do so.

In this visitation he appointed his son as his successor, to lead the chassidim as the next rebbe.