Blessed Tithers

MALACHI 3:10, 12
Bring ye all the tithes into the storehouse, that there may be meat in Mine house, and prove Me now herewith, saith the LORD of hosts, if I will not open you the windows of heaven, and pour you out a blessing, that there shall not be room enough to receive it.
And all nations shall call you blessed: for ye shall be a delightsome land, saith the LORD of hosts.

All blessings from God come with prerequisites. In order for God's people to receive this blessing, their tithes had to be put into God's storehouse, the treasury room in the sanctuary.
When this is done properly, God opens the windows of heaven and pours out a blessing upon His chosen and called people.
ISAIAH 44:3
"For I will pour water upon him that is thirsty, 
And floods upon the dry ground:
I will pour out My Spirit upon thy seed,
And My blessing upon thine offspring."

Then every nation will see that this holy nation is Blessed of the LORD. 
This is the last Blessing Of God that we see in the Old Testament.