Date: March 13, 2018 08:22PM
According to E.T. Benson, that's not necessary...
"The prophet does not have to say “Thus saith the Lord” to give us scripture.
Sometimes there are those who argue about words. They might say the prophet gave us counsel but that we are not obliged to follow it unless he says it is a commandment. But the Lord says of the Prophet, “Thou shalt give heed unto all his words and commandments which he shall give unto you.” (D&C 21:4.)
And speaking of taking counsel from the prophet, in D&C 108:1, the Lord states:
“Verily thus saith the Lord unto you, my servant Lyman: Your sins are forgiven you, because you have obeyed my voice in coming up hither this morning to receive counsel of him whom I have appointed.”
Said Brigham Young, “I have never yet preached a sermon and sent it out to the children of men, that they may not call scripture.” (Journal of Discourses, 13:95.)"https://www.lds.org/liahona/1981/06/fourteen-fundamentals-in-following-the-prophet?lang=eng
But then, of course, they don't consider things "prophets" said to be scripture -- including this thing that E.T. Benson said.