Charles Ellicott Commentary Zechariah 14:16

"And it shall come to pass, that every one that is left of all the nations that came against Jerusalem shall go up from year to year to worship the King, Jehovah of hosts, and to keep the feast of tabernacles." — Zechariah 14:16 (ASV)

Go up ... to worship. —The judgment on the nation is to be remedial. The result of it is to be that they will earnestly embrace the worship of the one only true God. “The Feast of Tabernacles” (lasting from the 15th to the 22nd of Tishri) is called par excellence “The Feast.” The chief object in its observance is, from a material point of view, the thanksgiving for the ingathering of the harvest and vintage. On the 21st (called Hosha’na Rabba), the Jews always pray that the coming year may not be one of drought.

It is most appropriate, then, that the prophet should represent the nations of the earth as joining the Jews in keeping their festival, which is that on which the Lord is especially praised as the beneficent God of nature. This prophecy is, of course, not to be taken literally. The prophet is merely foretelling in Old Testament language the future ingathering of the nations. Our Lord refers to the gathering of people into the kingdom of heaven as a harvesting (John 4:35).