And in this manner, we mention in the Musaf prayer of the Shalosh Regalim the past, present, and future, on which joy and gladness depend:

The past - "You have chosen us from all the nations, loved us and desired us, and elevated us, etc.," which is a past that continues into the present and causes us joy.

The present - "Because of our sins, we were exiled from our land and distanced, etc."

The future - "Rebuild Your house as in the beginning, and establish Your sanctuary on its site; let us witness its construction and rejoice in its restoration, and return the kohanim to their service, the Levites to their singing and music, and return Israel to their splendor, etc."

As stated, "festivals for joy," for the past and present, "holidays and times for gladness," to rejoice in the hope of the future.