Here is the full and correct quote by the correct person, Heber J. Grant.
"There is but one path of safety to the Latter-day Saints, and that is the path of duty. It is not testimony, it is not marvelous manifestations, it is not knowing that the Gospel of Jesus Christ is true, . . . it is not actually knowing that the Savior is the Redeemer, and that Joseph Smith was His prophet, that will save you and me, but it is the keeping of the commandments of God, the living the life of a Latter-day Saint."