Albert Barnes Commentary Zechariah 14:18

"And if the family of Egypt go not up, and come not, neither [shall it be] upon them; there shall be the plague wherewith Jehovah will smite the nations that go not up to keep the feast of tabernacles." — Zechariah 14:18 (ASV)

And if the family of Egypt do not go up, and do not come, who have no rain — Rather, “and there shall not be.” It may be that the prophet chose this elliptical form, knowing well that the symbol did not apply to Egypt, which, although it ultimately depended on the equatorial rains that overfilled the lakes supplying the Nile, did not need that precise arrangement of the autumn and spring rains essential to Palestine's fruitfulness. The omission leaves room for the somewhat prosaic addition by Jonathan, “The Nile shall not ascend to them.” More probably, the words are left undefined with intentional abruptness, “there shall not be upon them”—namely, whatever they need: the omission of the symbol in these two verses might more strongly suggest that it is only a symbol.

Egypt, the ancient oppressor of Israel, is united with Judah as one in the same worship of God, as Isaiah had said, In that day shall Israel be the third with Egypt and with Assyria (Isaiah 19:24); and since it is united in the duty, so also in the punishment for despising it.

Osorius: “Let Egypt not be proud that it is watered by the Nile, as if it needed no rain. That is, let no one be secure in this life. For though we stand by faith, yet we may fall. For although bedewed by the outflow of divine grace, and filled with its richness, yet if we do not give thanks continually for such great gifts, God will count us as the rest, to whom such copious goodness never came. The safety of all then lies in this: that while we are in these tabernacles, we cherish the divine benefits and unceasingly praise the Lord, who has heaped such benefits upon us.”

Cyril: “Under the one nation of the Egyptians, he understands those who are greatly deceived and chose idolatry most unreasonably, to whom it will be a grave, inevitable judgment, the pledge of destruction, that they despise the acceptable grace of salvation through Christ. For they are murderers of their own souls, if, when they could lay hold of eternal life and the divine gentleness (open to all who will choose it and put off the burden of sin), they die in their errors; the stain and pollution from transgression and error uncleansed, although the Divine Light illuminated all around and called those in darkness to receive sight. Of each of these I would say, Better is an untimely birth than he; for he cometh in with vanity, and departeth in darkness, and his name shall be covered with darkness (Ecclesiastes 6:3–4). Good had it been for them, if they had never been born (Matthew 26:24), is the Savior’s word.”

That this is not said of the Egyptians only, but will come true for all nations, who will be punished altogether if they are reckless of the salvation through Christ and do not honor His festival, he will establish in these words: