The נצי״ב was once asked why the salary of רבנים was so little in the past and their salary is so much greater in our own day. He answered: “As you know, לפי הדין its אסור for a רב to receive שכר and, accordingly, חז״ל enacted that he receive שכר בטלה. Thus, in the past, when רבנים would be learning יום ולילה and hardly being מבטל even an hour from תורה, their שכר בטלה was very little. But now that they are מבטלים הרבה מן התורה, their שכר בטלה is that much greater.”
06/10/2021