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.
Giving results in receiving. When we give even ten percent to God, He opens the windows of heaven and pours out a blessing so big that we do not have room enough to receive it. The figure of speech "open the windows of heaven" was used by God to describe the flood of Noah's time. That is the kind of abundant blessing God promises when we give.