Responsa sur Les Lamentations 4:26

And this week I developed a new explanation for Eichah Rabbah 4:24, which states that Rabbi Yehudah HaNasi learned Eichah on Shabbat which was the 9th of Av, and when he [accidentally] banged his finger, he said of himself, “There are many pains for the wicked. (Tehillim 32:10)” Rabbi Chiya responded, “The anointed of G-d is caught [only] due to ourcorruption.” (cf. Eichah 4:20) ... It appears to me that within our view that we push the fast to the 10th of Av, Shabbat is not Tishah b’Av at all, and one may learn with others, as Magen Avraham wrote; the day only has the status of the eve of Tishah b’Av. But if we held as Rabbi Yehudah HaNasi does, that once Tishah b’Av is pushed off, it should not be observed and it cannot be made up, then the observance of Tishah b’Av actually remains in place on the proper day, on Shabbat, and it is only that the mitzvah of Shabbat pleasure pushes off [fasting for] Tishah b’Av –but that which is private, learning with others and the like, are prohibited as they would be for any mourner on Shabbat. So Rabbi Yehudah HaNasi violated his own position ... And therefore he blamed banging his finger on this, and said of himself. “There are many pains,” and Rabbi Chiya responded, “We caused this, for we did not give in to you, and you did not wish to trespass the words of your colleagues.” ...