Backgrounds, heritage, and outside forces help people subconsciously make decisions and feel certain ways. Leonard Bernstein’s Jewish heritage had a huge and clear influence on both his compositions and thought processes. One of his earlier pieces was his “Symphony No. 3 Kaddish”. In Jewish tradition, “Kaddish” is recited in synagogues and is part of the mourning rituals during services. 
Bernstein’s “Kaddish” was dedicated to the memory of John. F Kennedy who was assassinated a few weeks prior to the first performance of Bernstein’s symphony. Interestingly enough, there is no mention of the word “death” ; however, there is mention of “life” multiple times throughout the piece.
To a certain degree, his symphony was a way in which Bernstein was able to explore his issues of his faith and connection to Judaism. Bernstein’s symphony has a very ominous tone; Kaddish begins in a minor key, modulates to a major key, and then returns to the original minor key for the ending. 
The final chord in this piece is a very dissonant chord, leaving the listeners filled with suspense and maybe even some agitation. Different keys and progressions all had to have been precisely decided by Bernstein in order to get his emotional point fully across. He incorporates very slashing, atonal and dramatic notes and aspects in this piece. Music is an incredibly emotional and thought-provoking form of art.
Bernstein uses his symphony to express his religious heritage and struggles, as well as loss and mourning. In the beginning of the symphony the speaker recites “I want to pray. I want to say Kaddish. My own Kaddish. 
There may be no one to say it after me. I have so little time, as You well know… Is there even time to consider the question? It could be here, while we are singing. That we may be stopped, once for all…”. (1) In Kaddish, Bernstein argues with God through his use of narration and powerful music.
Bernstein was a very proud Jew and had many connections to Israel and the Israel Philharmonic. 
Although we may never know how he truly felt about God and every aspect of Judaism, through viewing his life and his spiritual journey through his work, it is safe to say that Bernstein had a huge connection to Israel and to the Jewish people.
Sources:
(1)Jack Gottlieb, “Symphony No. 3: Kaddish (1963) https://leonardbernstein.com/works/view/48/symphony-no-3-kaddish