Explain the significance of what is described there, especially the fervor with which the Jews present

An anecdote about an event in Auschwitz appears on page 134 of Religions of the West Today

Explain the significance of what is described there, especially the fervor with which the Jews present “sang and danced and cried.”  Why is the knowledge of Sh’ma Yisrael (shema) by the young boy an occasion for such joy among the Jews in the death camp?  Be as specific as possible in explaining the meaning of this anecdote.

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