Q: The Zohar says that one should not touch his beard (Naso 130), Should one be strict in this regard?
A: According to the Zohar. Rav Kook said that Torah scholars should not trim or round-off their beard. Rav Chaim of Volozhin was asked about this and he said: "Look in my Zohar." The students looked there and next to "One should not touch his beard" was his emendation "with a razor," i.e. one should not touch his beard in the forbidden manner – with a razor (Igrot Re'eiyah vol. 2, p. 101).
Source: Parsha Sheet of R'Shlomo Aviner (Parashat Vayera 5769)