Joseph F. Smith
"By this principle (tithing) the loyalty of the people of this Church shall be put to the test. By this principle it shall be known who is for the kingdom of God and who is against it. By this principle it shall be seen whose hearts are set on doing the will of God and keeping His commandments, thereby sanctifying the land of Zion unto God, and who are opposed to this principle and have cut themselves off from the blessings of Zion. There is a great deal of importance connected with this principle, for by it shall be known whether we are faithful or unfaithful. In this respect it is as essential as faith in God, as repentance of sin, as baptism for the remission of sin, or as the laying on of hands for the gift of the Holy Ghost." (Conference Report, Apr. 1900, p. 47 as taken from Latter-day Commentary on the Book of Mormon compiled by K. Douglas Bassett, p. 452)