Malachi 3:4

וְעָרְבָה ה’ מִנְחַת יְהוּדָה וִירוּשָׁלִָם כִּימֵי עוֹלָם וּכְשָׁנִים קַדְמֹנִיֹּת

Then the offering of Judah and Jerusalem will be pleasant to Hashem as in the days of old and in ancient years.

This verse is the last line of the prayer following Shemoneh Esrei. When were these “good old days?” The Metzudas David explains that “days of old” refers to the time of Moshe and “ancient years” refers to the reign of King Solomon. There were times when sacrifices were so happily accepted by Hashem that He sent Heavenly fire to consume them.