Is it true that the Zohar's commentary on Deuteronomy 6:4 (the Shema) confirms the Christian doctrine of the Trinity?
Not at All! This is a trinitarian related fraud, possibly created by the founder of the American Board of Missions to the Jews (now known as the Chosen People Ministries), Itsak Leib Jaszovics, alias "Rabbi Leopold Cohn," a saloonkeeper, convicted of forgery in Hungary (For further information see, David Max Eichhorn, Evangelizing the American Jew, Middle Village, New York: Jonathan David Publishers, 1978, pp. 172-174.). The claim that the Zohar's commentary on Deuteronomy 6:4 confirms the Christian doctrine of the Trinity is based on a spurious passage attributed to that volume. It appears in Cohn's tract, Do Christians Worship Three Gods? (pp. 4-5), published by the Chosen People Ministries. On the basis of his forgery, Cohn concluded that "According to the Zohar the Messiah is not only called Jehovah but is a very part of the triune Jehovah" (p. 5). This forgery is also perpetuated in the literature of the Jews for Jesus missionary organization. Using Cohn's spurious passage, Arnold Fruchtenbaum, a born-Jewish Christian missionary, writes:
The Zohar, the great book of Jewish mysticism, recognized the concept of plurality in the Shema and commented as follows: Why is there need of mentioning the name of God three times in the verse? The first is the Father above. The second is the stem of Jesse, the Messiah who is to come from the family of Jesse through David. And the third one is the one which is below (meaning the Holy Spirit who shows us the way) and these three are one. (Arnold Fruchtenbaum, Jewishness and the Trinity, San Francisco: Jews for Jesus, 1978, p. 8. This article was first published in the Jews for Jesus publication Issues: A Jewish Christian Perspective, 1:8, 1978).
Fruchtenbaum quotes faithfully Cohn's fraudulent passage. However, a simple examination of the relevant Zohar commentary on the Shema reveals that no such text exists in the Zohar. It should be noted that many other missionary organizations have quoted Cohn's forgery in their literature.