Any rebbi worth having does not let go until there is someone to take over. (And many of the rabbiem will not let go even then.) I know personally of rabbeim in yeshivos in America that have kept up with the bochurim scheduled to leave, and with those who’ve already left, were in Israel for a year or two and were just home for Pesach and couldn’t return. Sure, there are challenges. But our rabbeim and roshei yeshiva are not achzarim who kiss their talmidim good bye and then wash their hands of them.
Menu