Dallin H Oaks said:
No prophet of the Lord in modern times has preached the law of tithing more fervently than Heber J. Grant. As an Apostle and later as President of the Church, he frequently called upon the Saints to pay an honest tithe and made firm promises to those who would do so.
In a general conference in 1912, Elder Heber J. Grant declared:
“I bear witness — and I know that the witness I bear is true — that the men and the women who have been absolutely honest with God, who have paid their tithing, … God has given them wisdom whereby they have been able to utilize the remaining nine-tenths, and it has been of greater value to them, and they have accomplished more with it than they would if they had not been honest with the Lord” (in Conference Report, Apr. 1912, p. 30).
In 1929, President Heber J. Grant said:
“I appeal to the Latter-day Saints to be honest with the Lord and I promise them that peace, prosperity and financial success will attend those who are honest with our Heavenly Father. … When we set our hearts upon the things of this world and fail to be strictly honest with the Lord we do not grow in the light and power and strength of the gospel as we otherwise would do” (in Conference Report, Oct. 1929, pp. 4 – 5).
During the Great Depression, President Grant continued to remind the Saints that the payment of tithing would open the windows of heaven for blessings needed by the faithful. In that stressful period, some of our bishops observed that members who paid their tithing were able to support their families more effectively than those who did not. The tithe payers tended to keep their employment, enjoy good health, and be free from the most devastating effects of economic and spiritual depression (see Church News, 9 Dec. 1961, p. 16). Countless tithe-paying Latter-day Saints can testify to similar blessings today.
I am grateful to President Grant and other prophets for teaching the principle of tithing to my parents and to them for teaching it to me.
Talk Source: https://www.lds.org/general-conference/1994/04/tithing?lang=eng