The word of our testimony is one of the factors by which we overcome the world. I have the testimony that the only times I have suffered financially since becoming a Christian were when I neglected to tithe. This was usually done out of carelessness because I have always believed in tithing. However, every time I have suffered financial trouble and have gone back and checked my records, I found that my troubles began when I became careless in this one thing. When I repented and started giving the firstfruits of my income to the Lord again, the windows of heaven always quickly opened just as He promised.
From the book "Once Saved, Always Saved"