Yerushalmi Taanis 1:1 says: א"ר לוי אילו היו ישראל משמרין שבת אחת כתיקנה מיד היה בן דוד בא R. Levi said: If Israel kept one Shabbos correctly, the son of David would immediately come. But ...
does anyone have a source for the suggestion that If all Israel respected the Sabbath if only one single day, the Messiah would come immediately, for it is written: “Today if you were to listen to his ...
We have a tradition that Tisha B'Av will become a holiday in the time of Moshiach. Will that holiday also be nidcheh if it comes out on Shabbos?