"And Pinchas the son of Elazar saw" (Bamidbar 25:7)
Pinchas endangered not only his body (the tribe of Simeon threatened to kill him) but also his soul (what he did was against the sages' will), all to remove G-d's wrath from the people.
Once, a fire broke out at the home of the Alter Rebbe, and one booklet of Chassidus was burnt. After the fire was extinguished, the Rebbe asked if anyone had studied the booklet. His son, the Mittler Rebbe, answered: But father, you had written on it, 'No one should open this book, not in this world, and not in the world to come!' The Rebbe replied: Where is your mesirus nefesh - your total desire, to the point of self-sacrifice - for Chassidus..?
(Likkutei Sichot 18, p. 319)
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