From Latter-day Prophets:
Lorenzo Snow

Wherefore, I the Lord … called upon my servant Joseph Smith, Jun., and spake unto him from heaven, and gave him commandments; … That mine everlasting covenant might be established; That the fulness of my gospel might be proclaimed (D&C 1:17, 22–23).

Lorenzo Snow

As a young man, Lorenzo Snow met Joseph Smith and was baptized into the Church. He was one of the last Presidents of the Church to personally know the Prophet. President Snow often bore his testimony about the Prophet Joseph and how Heavenly Father restored the true Church of Jesus Christ through him. (Lorenzo Snow by Lewis A. Ramsey.)

A word or two about Joseph Smith. Perhaps there are very few men now living who were so well acquainted with Joseph Smith the Prophet as I was. I was with him oftentimes. I visited him in his family, sat at his table, associated with him under various circumstances, and had private interviews with him for counsel.

I know that Joseph Smith was a Prophet of God; I know that he was an honorable man, a moral man, and that he had the respect of those who were acquainted with him. The Lord has shown me most clearly and completely that he was a Prophet of God, and that he held the Holy Priesthood and the authority to baptize people for the remission of their sins and to lay hands upon them for the reception of the Holy Ghost, that they might receive a knowledge themselves in relation to these things.

I am one that has received from the Lord the strongest revelation concerning the truth of this work. That manifestation was with me powerfully for hours and hours; and whatever circumstances may occur in life, as long as memory lasts this perfect knowledge will remain with me.

I shall never forget the first time I saw Joseph Smith. It was in Father Johnson’s house, in the township of Hiram, in the State of Ohio, about twenty-five miles from Kirtland. … When I saw him he was standing in the doorway. Before him was a small bowery occupied by about a hundred and fifty or two hundred men and women. There for the first time I heard his voice. When I heard his testimony in regard to what the Lord had revealed to him, it seemed to me that he must be an honest man. He talked and looked like an honest man. He was an honest man.
(Conference Report, October 1900, page 61; paragraphing added.)

Brother Joseph by David Lindsley