I recently received an email from Ruth Almagor-Ramon, the editor of Kol Yisrael’s program
Rega shel Ivrit. She wished me "Yishar Koah" on this blog. That's quite an honor - so I figured the best way to repay her would be to write an entry on that phrase.
Yishar Koah, or Yasher Koach, יישר כח means congratulations. My cousin, Rabbi Ephraim Mirvis, writes about it here:
When congratulating someone who has had the merit of performing a mitzvah or other worthy task in Shul, we say Yasher Koach, or the shortened form of Shkoach.The words literally mean, "May your strength be firm". The first reference is in the Talmud (Shabbat 87a), quoted in Rashi's concluding commentary on the Torah. When Hashem refers to the first tablets of the Decalogue which Moses broke, He mentions asher shibarta - the tablets which you broke. In a play on the word asher, our Rabbis explain that it was as if Hashem was saying to Moses, Yasher Koach for breaking the tablets! Moses here received Divine appreciation for the way in which he reacted to the nation's worship of the Golden Calf.Yasher Koach was originally intended to be used exclusively for one who had read from the Torah. Scholars explain that in ancient times, the Torah scroll was held upright during its reading so that those surrounding it could follow as it was being read (in pre-printing press days, Synagogues did not have many Chumashim). With this in mind, Sephardi communities made Sifrei Torah in cylindrical cases, which were self-standing. In Ashkenazi Synagogues, however, the Ba'al Koreh required a lot of strength to keep the Torah scroll upright while he was reading from it and often he was helped by those standing alongside him. We can now understand why he, in particular, was blessed with Yasher Koach - may your strength be firm!
Eliezer Segal also explains the history of the phrase here, and points out the irony that while we use the phrase to wish strength for those holding the Torah, the original midrash refers to a case where the Torah was thrown down.