לע"נ האשה רות בת ר' צבי יהודה ע"ה - יום השנה – ז' כסלו
There is a Machlokes Tanaim if Gid Hanashe is Muter or Asur Behanha
(benefit) Reb Yehuda holds that it is Muter and Reb Shimon holds it is Asur.
The Bais Yosef (Y.D. 65) holds that is best to refrain from having Hanaha
from the Gid Hanasha because The Zohar (Parshas Vayishlach) writes
that it is Asur Behanha.
The Rema in Darkei Moshe writes, he heard that the author of
The Zohar was R. Shimon (Bar Yochai) who is mentioned in the Talmud.
If that is the case, why care that the Zohar holds that it is Asur.
The Gemoro (Eruvin 46b) rules, where there is a Machlokes between R. Shimon and Reb Yehuda the Halacha is like R. Yehuda
For a detailed discussion if Reb Shimon Ben Yochai wrote the zohar click HERE