(Exodus 23:16) refers to Shavuot (the Festival of Weeks)h as "the festival of the harvest, the first-fruits of your labor." The Mekhilta notes that this description appears within a section about the shemitah year — the sabbatical year when all agricultural work ceases. Why mention harvest festivals in the context of a year without harvesting?
The answer teaches a crucial principle: even during the shemitah year, the three pilgrimage festivals are not displaced from their proper times. Although the shemitah suspends planting, harvesting, and all agricultural operations, the festivals that correspond to those agricultural milestones remain on schedule.
Passover falls at the time of the spring barley harvest. Shavuoth falls at the time of the wheat harvest. Sukkot (the Festival of Tabernacles)h falls at the time of the autumn ingathering. In an ordinary year, these festivals align with actual agricultural events. During the shemitah, no harvesting takes place — but the festivals are still observed on their original dates.
The Mekhilta's ruling separates the calendar from the agriculture. The festivals were historically rooted in the farming cycle, but their observance transcends it. Even when the fields lie fallow, Israel still gathers for Passover, Shavuoth, and Sukkoth at the same times. The festivals commemorate divine encounters, not human labor. They continue because God continues to meet His people on these appointed dates, whether or not the fields are producing.