What is actually evinced by, "returning to this world as a
Gilgul," as it is described and attributed to RAV CHAIM VITAL, in the name of the ARIZAL (cited in Insights to the Daf to Chulin 139:3)?
>>It is interesting to note that the ARIZAL (quoted by RAV CHAIM VITAL in his introduction to Sha'ar ha'Mitzvos; Birkei Yosef, Gilyon Shulchan Aruch YD 292:6, and Aruch ha'Shulchan YD 292:1) writes that according to Kabalah, one must make every effort to perform Shilu'ach ha'Ken. He adds that one who does not perform the Mitzvah of Shilu'ach ha'Ken will return to this world as a Gilgul.)<<
The concept of Gilgul, or reincarnation, is a central feature of the teachings of the Arizal. Although it appears earlier in the Zohar, there are no genuine sources for it in the Talmud or Chazal and many early authorities did not accept such a concept.
The concept is hinted at in a number of sources. Iyov says that "I left my mother's womb naked and will return there naked," implying that he expects his soul to be reincarnated. Koheles writes that "a generation goes and a generation comes," instead of the other way round, implying that the same generation of souls rejuvenates again.
The idea is that every soul needs to reach its rectification while it is in this world but most souls do not succeed in doing so the first time they are sent and therefore must be reincarnated in another person. This would also solve the major religious dilemma of reward and punishment, as it would explain why righteous people or babies suffer and die before their time, if they have thus achieved the final rectification of their souls.
Other souls may require a number of reincarnations, with the maximum being four according to the Kabalah of the Arizal. There is also a possibility that a part of the soul, known as a Nitzotz or spark, will be reincarnated in another person.