From Latter-day Prophets:
Joseph F. Smith

The prophet … holds the keys of priesthood pow’r today (Hymns, no. 22).

President Joseph F. Smith was the nephew of Joseph Smith, the first President of the Church, and the father of Joseph Fielding Smith, the tenth President of the Church. When Joseph F. Smith was the President, he said this about all of the prophets he had known.

I bear my testimony to you and to the world, that Joseph Smith was raised up by the power of God to lay the foundations of this great Latter-day work, to reveal the fulness of the gospel to the world in this dispensation, to restore the priesthood of God to the world, by which men may act in the name of the Father, and of the Son, and of the Holy Ghost, and it will be accepted of God; it will be by His authority. I bear my testimony to it; I know that it is true.

I bear my testimony to the divine authority of those who have succeeded the Prophet Joseph Smith in the presidency of this Church. They were men of God. I knew them; … so I can bear testimony to the integrity, to the honor, to the purity of life, to the intelligence, and to the divinity of the mission and calling of Brigham [Young], of John [Taylor], of Wilford [Woodruff], and of Lorenzo [Snow]. They were inspired of God to fill the mission to which they were called, and I know it. I thank God for that testimony.
(Conference Report, October 1910, pages 4–5.)