Haggai 1:9
You have looked for much, and, lo, it came to little; and when you brought it home, I blew it away. Why? says the Lord of hosts. Because of my house that lies in ruins, while you busy yourselves each with his own house.

The exiles who returned from Babylon got a bit distracted.  They were delivered from captivity in order to worship their God.  But they got caught up in the work of re-building their houses and farms and businesses and forgot the main thing: rebuilding the Temple of God.  And for all their efforts, it just didn’t seem to be coming together as it should.  They couldn’t figure out why.  Haggai was sent to remind them.  His point was the same as a later Messenger to the people of Israel, “Seek seek first His kingdom and His righteousness, and all these things shall be yours as well” (Matthew 6:33).