When God takes note of Judah's uncleanness, and her disastrous focus—idolatry—His promised blessing will be the means by which He will turn those things around. He will restore Israel's and Judah's lands and cities to them, and He will give them the definitive Governor and the ultimate High Priest. Zerubbabel and Joshua are just types of what will be fulfilled later by Christ.
When we understand this, we can better understand the imagery in Haggai 2:19: “Is the seed still in the barn? As yet the vine, the fig tree, the pomegranate, and the olive tree have not yielded fruit. But from this day I will bless you.”
Recall that Kislev 24 is in the winter, a time of short days and long nights. Farmers have long completed their harvesting, and everyone hopes that they have stored away enough to last until the vines, trees, and crops begin producing fruit again. Remember, also, that this particular harvest was probably sparse because of God's curse on their crops.
Winter, even in a good year, is not usually a time of blessing. It is often a difficult time, one of making use of the blessings that came in previous seasons. Yet God chose this specific date, which in some years could even be the shortest day of the year. He selected this bleakest of times to start His blessing—a blessing whose highest fulfillment will be found in the work and sacrifice of Jesus Christ.
This scenario sets up an intriguing possibility. We know that Jesus was born sometime in the fall. If we count back nine months from the fall, we arrive at a date in winter. Is it possible, then, that Kislev 24 is the date when the power of the Most High God overshadowed Mary and caused her to conceive the Messiah (Luke 1:35)?
Verse 19 contains a curious play on words that may support this possibility. A question is asked, “Is the seed still in the barn?” The word translated as “seed” is also rendered “child” or “posterity.” Remember that Zerubbabel means “seed of Babylon,” but also recall that when God tells Abraham, “In your seed all the nations of the earth shall be blessed” (Genesis 22:18; 28:14; emphasis ours), the Seed to which He refers is Jesus Christ, forty-two generations later (see also John 7:42; Romans 1:3; Galatians 3:16, 19).
Haggai 2:19 describes a time when the seeds from the previous harvest are not in the barn because they have been planted, but it is before any fruit was produced. It could also, then, describe a Child who has been conceived, but not yet born—and through that Child the blessing on Judah and Israel, the church, and eventually, the entire world would come. Again, this is speculation, but Jesus' conception on this date could be another application of what God means when He says, “from this day I will bless.”
However, regardless of whether this speculation is correct, we see that God is incredibly active in the lives of His people and quite willing to shake heaven and earth to bless. Yes, God gives physical blessings, but the far more meaningful ones are not material in nature.