Charles Ellicott Commentary Exodus 23:14-17

"Three times thou shalt keep a feast unto me in the year. The feast of unleavened bread shalt thou keep: seven days thou shalt eat unleavened bread, as I commanded thee, at the time appointed in the month Abib (for in it thou camest out from Egypt); and none shall appear before me empty: and the feast of harvest, the first-fruits of thy labors, which thou sowest in the field: and the feast of ingathering, at the end of the year, when thou gatherest in thy labors out of the field. Three times in the year all thy males shall appear before the Lord Jehovah." — Exodus 23:14-17 (ASV)

The first great festival—the Passover festival—had already been instituted (Exodus 12:3–20; Exodus 13:3–10). It pleased the Divine Legislator at this time to add to that festival two others, and to make all three equally obligatory. There is some reason to suppose that, in their early stages, the “feast of harvest” and the “feast of ingathering” already existed. All nations, from the earliest time to which history reaches back, had festival seasons of a religious character; and no seasons are more suitable for such festivities than the conclusion of the grain harvest and the final completion of the entire harvest of the year. At any rate, whatever the previous practice, these three festival seasons were now laid down as essential parts of the Law, and continued—supplemented by two others—the national festivals as long as Israel was a nation.

In other countries, such seasons were more common. Herodotus says that the Egyptians had six great yearly festival times (ii. 59); and in Greece and Rome, there was never a month without some notable religious festivity. Such institutions exerted a political as well as a religious influence, and contributed to national unity. This was especially the case when, as in the present instance, they were expressly made gatherings of the whole nation to a single centre. What the great Greek festivals (Olympic, Pythian, etc.) were to Hellas, the three great annual gatherings to the place where God had fixed His name were to Israel—a means of drawing the national bond closer and counteracting those separatist tendencies that a nation split into tribes almost necessarily developed.