from RaisinSoul...


It is an obligation to visit one's Rebbi on the Holiday (Sukah 27:b)

RAV YONASAN EIBESHITZ (Ya'aros Devash 1:12 and elsewhere) explains that during the times of the Beis ha'Mikdash (when Elisha lived), everyone would go to greet the presence of the Shechinah in Yerushalayim. They would visit the Rebbi only on Shabbos and Rosh Chodesh, when there was no requirement to go to Yerushalayim. After the Churban, the practice was instituted to visit the Rebbi in place of going to Yerushalayim, because a Talmid Chacham reflects the presence of the Shechinah.