In response to Just Another Yid who asked “Is there a source for the Psak Din, following are some sources:
See Shaalos u’Teshuvos Minchas Yitzchok (vol. 4, section 113) where the Minchas Yitzchok, one of the greatest Poskim of our times, wrote: “I searched the works of the great Acharonim in the hope of finding a halachic basis to defend the practice of allowing [the use of electric shavers], but not only did I not find a source to be lenient, on the contrary — I found that they all agree to be stringent [and prohibit shaving machines].”
Rav Elyashiv zt’l wrote in a teshuvah published in his sefer Kovetz Teshuvos (vol. 1, section 32) that the electric shavers of today are unquestionably infinitely Halachicly worse than those that existed in the time of the Chofetz Chaim and were prohibited by him, because modern machines shave much more closely to the skin, and shaving with them is an “issur Torah mamosh” — a definite and absolute Torah prohibition (and not just a “sofek issur d’oraysa”).
Rav Chaim Kanievsky shlita wrote in the name of his father, the Steipler Gaon zt’l: “It has already been publicized that the Chofetz Chaim zt’l in Likkutei Halachos on Makkos prohibited even manual (non-electric) shaving machines; how much more so are today’s electric shavers forbidden since they are more advanced.”
Rav Shach zt’l wrote (Michtavim U’Maamarim 3:75): “To the questioner, may he be well: Concerning shaving the beard with electric shaving machines — see the sefer Likkutei Halachos on tractate Makkos (by the Chofetz Chaim), p. 14b (Ein Mishpat op. cit.), where he writes that it is prohibited, and one may not be lenient in this matter. It is also well-known that the Chazon Ish zt’l ruled that the use of all shaving machines is forbidden. This is my response, (signed) Elazar Menachem M. Shach.”
Similarly, the Debretziner Rov writes in Shaalos u’Teshuvos Be’er Moshe (vol. 7, Kuntres Electric 2:18) that today’s shaving machines are “one hundred percent more halachically severe than the machines referred to by the Chofetz Chaim.”
In the most recently published volume of responsa Shevet HaLevi (vol. 11, Y.D. section 198), Rav Shmuel Halevi Wosner zt’l wrote: “With regard to shaving machines…it was agreed by ALL the Geonim…that there is no difference between [using] them and [using] a razor… The Gaon R. Moshe Feinstein sought to make a distinction between today’s [shaving machines] and a razor and advanced a theory [in justification]…. That theory is not correct and has not been accepted ( אינה נכונה ולא נתקבלה aynah nechonah v’lo niskablah).”
Rav Yaakov Kamenetzky zt’l (who was certainly familiar with Rav Moshe Feinstein’s position regarding shaving with electric shavers), in his sefer Emes l’Yaakov on Shulchan Aruch (Y.D. 181), Rav Yaakov Kamenetzky zt’l wrote (to his grandson) that there is no mesorah from the Rabbonim in America that can be relied upon to permit the use of electric shavers. To quote Rav Yaakov Kamenetzky zt’l: “Regarding [the prohibition of using] machines to shave [the beard], this is not just a chumra [halachic strictness] but a substantive [halachic] issue…. In fact, I do not know whether the great Torah authorities (Gedolim) of America [ever] explicitly permitted them; it is possible that they kept silent because no one asked them [their opinion], and they avoided the issue, knowing that their words would not be heeded…. It is difficult to rely upon [any] tradition (mesorah) [to be lenient].”
See Halichos Shlomo (tefilah, 2:7, note 24) where Rav Shlomo Zalman Auerbach zt’l ruled that one cannot rely on any heter granted by any Rov for any shaving machine of past generations, since those machines did not cut the facial hair as close to the skin and did not produce as clean of a shave as contemporary shavers do. See further in Halichos Shlomo (ibid.) where a letter from Rav Shlomo Zalman Auerbach zt’l to the author of the sefer Hadras Ponim Zokon is quoted, stating: “In my humble opinion, by publishing this sefer you are accomplishing something positive and beneficial. Perhaps through this sefer the issues will be elucidated and clarified, thereby saving the Jewish public from a severe transgression.”