To those who stubbornly claim that there is “no basis for this ‘chumra’ ” and try to convince other not to be concerned over this inyan which impact shmiras shabbos –
Below are TWO concurring sources of a posek hador and a renown Talmid Chochom, Rav S.Z. Auerbach and Harav Moshe Shternbuch. I accept these as better halachic authorities than Health, b’michilas kvodo.
The seforim of these gedolim are cited below and can be looked up by anyone who can read Hebrew without nekudos.
See http://e.yeshiva.org.il/ask/?id=2968:
Question:
Is it proper to extend greetings of Shabbat Shalom (Gut Shabbos) on Friday prior to Mincha?
Answer:
[Zachor et Yom HaShabbat]
[The Halacha is that Biblical Mitzvot require intention (Kavana) for observance. See Shulchan Aruch Orech Chayyim 60:4]
[an hour and fifteen minutes prior to sunset on a day wherein there are twelve daytime hours]
Rabbi J. Simcha Cohen
Now you know WHEN it’s time to say Gut Shabbos…as Reb Abie Rotenberg sings.