The shutting up of the heavens means drought (2 Chronicles 7:13). Sometimes the opening of the windows of heaven is a curse which leads to a devastating flood (Genesis 7:11, Isaiah 24:18). In our text, however, the opening of heaven is a blessing of sufficient rain to water the fields and fill the wells.
10 Bring the full tithe into the storehouse, that there may be food in my house. And thereby put me to the test, says the LORD of hosts, if I will not open the windows of heaven for you and pour down for you a blessing until there is no more need.