Musar su Lamentazioni 1:15

There is an allusion to this in the Torah: When Aaron said (concerning the next day which was the 17th of Tammuz) חג לה' מחר "tomorrow there will be a holiday to G–d" (Exodus 32,5). The term מחר, need not always refer to the day immediately following it. It may, on occasion, refer to a time in the distant future. Aaron hinted that the time would come when even a day that is a fast-day today, such as the day that Moses had occasion to smash the tablets with the Ten Commandments G–d had given him, i.e. the day after Aaron's pronouncement, would be turned into a happy occasion. It is no accident then that our calendar is arranged in such a way that the ninth day of Av always occurs on the same day of the week as the first day of Passover, the day we commemorate the Exodus from Egypt. That redemption had been the real beginning of the eventual and enduring redemption of the Jewish people. This is why the prophet Michah (7,15) says כימי צאתך מארץ מצרים "just as during the days when you came out of Egypt." The prophet introduces a vision of the redemption of the future by speaking of great miracles yet to be performed.