President Heber J. Grant testified that
“if the people will pay their tithes and offerings, they will not only be blessed in their material affairs, but they will be abundantly blessed with increased outpouring of the Spirit of the Lord”
(Gospel Standards, p. 106).
This is a part of the promise the Lord made through his servant Malachi. The Lord will not only open the windows of heaven and pour down spiritual blessings, but he will also preserve our fruits and vegetables—the labor of our hands—from destruction as well (see Malachi 3:8–12).
Concerning our fast offerings, President Marion G. Romney said:
“One of the important things the Lord has told us to do is to be liberal in our payment of fast offerings. I would like you to know that there are great rewards for so doing—both spiritual and temporal rewards. The Lord says that the efficacy of our prayers depends upon our liberality to the poor”
(in Conference Report, Mar.–Apr. 1979, p. 135; or Ensign, May 1979, p. 95).