"Bring the whole tithe into the storehouse, that there may be food in my house. Test me in this,” says the LORD Almighty, “and see if I will not throw open the floodgates of heaven and pour out so much blessing that there will not be room enough to store it."
What God's people used to tithe was not money, but 10% of their crops every harvest which would be kept in the storehouse to feed the priests and the poor. As God has blessed you, so in turn do you return to him what he has given so that others may be blessed as well. However in the 2 verses preceding this one, we learn that those who do not tithe are thieves.
They rob God who deny him his tithe because they deny his the poor of their sustenance and the priests of their wages. Of such Paul says this ,"He who has been stealing must steal no longer, but must work, doing something useful with his own hands, that he may have something to share with those in need." (Ephesians 4:28). So the opposite of stealing is generosity. Where you used to take for yourself, now you give to others.
And what is the result of generosity? Even more generosity from our Father in heaven as he throws open the floodgates of heaven and pours out blessing until your cup runneth over. Test God in this and see if he won't do as He says.