Rabbi Yossi says, "A merit ends up being on a day of merit and a punishment ends up being on a day of punishment. For you will find to say that when the First Temple was destroyed, that day was the culmination of the Shabbat, and it was at the culmination of the sabbatical year and it was during the watch of Yehoyariv and it was the ninth of Av. And likewise with the Second. And in both this one and that one, the Levites were standing on the platform and reciting song. And what song did they recite? 'He will make their evil recoil upon them' (Psalms 94:23)."