The President of the Church Is the Only Man on the Earth Whom the Lord Has Authorized to Exercise All of the Keys of the Kingdom of God

Doctrine and Covenants 112:15

15 Exalt not yourselves; rebel not against my servant Joseph; for verily I say unto you, I am with him, and my hand shall be over him; and the keys which I have given unto him, and also to youward, shall not be taken from him till I come.

President Brigham Young said:

“I do not care who leads the Church, even though it were Ann Lee; but one thing I must know, and that is what God says about it. I have the keys and the means of obtaining the mind of God on the subject. I know there are those in our midst who will seek the lives of the Twelve as they did the lives of Joseph and Hyrum. We shall ordain others and give the fulness of the priesthood, so that if we are killed the fulness of the priesthood may remain. Joseph conferred upon our heads all the keys and powers belonging to the apostleship which he himself held before he was taken away, and no man or set of men can get between Joseph and the Twelve in this world or in the world to come. How often has Joseph said to the Twelve, ‘I have laid the foundation and you must build thereon, for upon your shoulders the kingdom rests.’”

(History of the Church, 7:230.)