This is the quintessential question of Lubavitchers on mivtzoim.
There is even a book with this title, full of great stories from mivtzoim.
One of the most draining forms of mivtzoim is of course, Rosh Hashana, when you walk far distances in the heat, and then you have to blow the shofar a bunch of times.
As I passed a bus stop, I asked the guys there if they were Jewish.
Hmmmm. I slowed down and faced him. "How sort of?"
" I'm Catholic," he explained, "and I have some Jewish friends."
"Right. Well have a nice day."
An Eagle Among Turkeys
4 days ago