And the Lord said unto me, John, my beloved, what do you desire? For if you shall ask what you will, it shall be granted unto you. And I said unto him, Lord, give unto me power over death, that I may live and bring souls unto you. And the Lord said unto me, Verily, verily I say unto you, because you desired this, you shall tarry until I come in my glory, and shall prophesy before nations, kindreds, tongues, and people.
And for this cause the Lord said unto Peter, If I will that he tarry till I come, what is that to you? For he desired of me that he might bring souls unto me, but you desired that you might speedily come unto me in my kingdom. I say unto you, Peter, this was a good desire, but my beloved has desired that he might do more, or a greater work yet among men, than what he has before done; yea, he has undertaken a greater work. Therefore, I will make him as flaming fire and a ministering angel. He shall minister for those who shall be heirs of salvation who dwell on the earth, and I will make you to minister for him and for your brother James [Jacob].
Source: JSH 13:18-19
Although there are those who will absolutely cry heresy and throw dirt on their hair and tear their clothes because they are scholars, and they are bona fide, and they know I’m talking out of my hat—but I’d remind you that Joseph talked out of his hat, too—that fourth and missing, unmentioned angel, Uriel, in mortality was known to us as John, the one who was beloved of the Lord. … And Uriel, though not mentioned, is the one who in the North has the power over the earth, which is apt, because he remains upon the earth, and he is the guardian at one gate with Elijah at the other end.