Joseph F. Smith, Masterpieces of Latter-day Saint Leaders, comp. N. B. Lundwall, 1953, p. 78

I would like my children, and all the children of Zion, to know that there is nothing in this world that is of so much value to them as the knowledge of the gospel as it has been restored to the earth in these latter days through the Prophet Joseph Smith. There is nothing that can compensate for its loss. There is nothing on earth that can compare with the excellency of the knowledge of Jesus Christ. Let, therefore, all the parents in Zion look after their children, and teach them the principles of the gospel, and strive as far as possible to get them to do their duty—not mechanically, because they are urged to do it, but try to instill into the hearts of the children the spirit of truth and an abiding love for the gospel, that they may not only do their duty because it is pleasing to their parents, but because it is pleasing also to themselves.

I found this quote while reading an Ensign Article from Elder L. Tom Perry called "Therefore I Was Taught," May 1994