To give those of you some background about the timeline of Haggai (for those who haven't read it recently), Haggai lived right after Ezra brought everyone back to Israel from Babylon. Although they had restored the Holy of Holies, they hadn't completed the remaining parts of the temple but spent the time rebuilding their crops, houses, and family connections. At the beginning of Haggai, God speaks to both Haggai and Joshua, the high priest, about re-establishing the House of God. It is the first day of the 6th month, and God asks His people if they have noticed that though they eat, drink, sleep, etc, they are never satisfied. Why? The answer is because they haven't done God's work first. If they were to build the House of God first, then God would bless them and they would finally feel full, well rested, and quenched. Since 6 is the number signifying incompletion, or "just not quite good enough", Haggai uses the number to help the people understand that by themselves, they will never be good enough. They need to honor God, and keep themselves God-focused.
The second chapter begins in the 7th month and the 21st day, a combination of the number for perfection, 7, and the number of stability, 3. When the perfect number shows itself, we usually see a meeting of the mortal with the Divine, such as the ending of the initial Creation story. In Haggai, the pattern is no different. God asks the people to look at the House of God they've rebuilt, and how dull it is compared to its finer days in history. He then tells them that he will bless them and bring forth the wealth of the surrounding areas to provide the glory for His House. Thus, God demonstrated His power and dominion over the earth, and His providence for His own people.
Lastly, in the middle of chapter 2, God meets with Haggai and the priests again to give them one last blessing for the current time. Although it is only a couple of months later, the Israelites have built a magnificent House of God, and God is weel pleased. It is now the 9th month and the 24th day (3 months exactly from the time they started!), and God tells the people that because they have done what He asked, He will bless them from that day forward. Since there are 30-31 days average in a month, the 24th day is roughly 3/4 of the way through the month... we have 9 3/4! Although not an alchemically significant number, the 9 3/4 is significant in the world of Harry Potter. Platform 9 3/4 is the name of the train platform for the Hogwarts Express, the train that takes Harry into the magical world from Kings Cross Station.
Perhaps JK Rowling did not realize how much her Platform 9 3/4 came from the Bible, but the parallel is there: once Harry gets to Platform 9 3/4, his life becomes one of blessings and not curses; one of a full stomach, not one who knows starvation; one full of people who love and honor him, not one where those who should love him disgrace him and negate his existence at every turn. Harry had to make a decision midway through "Deathly Hallows": should he continue on as Dumbledore told him and destroy the Horcruxes, or should he follow his own path and get the Deathly Hallows? He chose to do as he was told, and in the process, gained the Deathly Hallows. The Israelites learned the same lesson, more than 2500 years ago - do God's work first, then He will bless you with your own desires met and love to suffice all your needs.