Likutei Moharan 26:1/ליקוטי מוהר"ן כ״ו:א׳

1“A Retzitza (chick) that dies in its shell, through where does the spirit-of-life exit ?” He said to them, “Through where it entered” (Bekhorot 8b).

2A chick — This is an eFRoaCh, the concept of tzaddik: <“A tzaddik, like a date palm, yiFRaCh (will flourish)” (Psalms 92:13) ; and as in,> “In his days, the tzaddik yiFRaCh” (Psalms 72:7).

3[The Wise Men of Athens] asked him: The tzaddik who kills himself and sacrifices his soul in prayer and entreaties, in which place in the prayer does he especially have to sacrifice his soul?

4And [Rabbi Yehoshua] answered them:

5Through where it entered — Namely, wherever he has to elevate the sparks of holiness. In other words, wherever external thoughts enter into him <he has to elevate them. This is because the external thoughts are actually the fallen sparks of holiness,> and he has to elevate them, as is known. That is where he has to sacrifice his soul. A chick that dies - a chick that perishes inside its shell: