Who Are Angels?

D&C 130:5

    But there are no angels who minister to this earth but those who do belong or have belonged to it.

Joseph Fielding Smith
    There is a prevailing idea today, which arose during the centuries of apostasy, that angels are superior to human beings in their nature–in fact, that they belong to an entirely distinct and different race.  Angels are ministering servants who carry messages from our Eternal Father and his Son Jesus Christ. All angels coming to Adam after the fall were spirits belonging to this earth who had not yet obtained bodies of flesh and bones. After men had been translated as was Enoch, they, as translated beings, could and did come to minister unto the prophets. (Answers to Gospel Questions, 2:98)

George Q. Cannon   
    We have no doubt of the correctness of the statement of the Prophet Joseph Smith that “there are no angels who minister to this earth but those who do belong or have belonged to it” (D&C 130:5); but that does not necessarily imply that they did not belong to the earth before they took a mortal body. In our opinion they belonged to this earth from the time of its creation, when they covenanted to come and take bodies thereon, at the time that the morning stars sang together and all the sons of God shouted for joy. (Gospel Truth, p. 54)

Joseph F. Smith
    We are told by the Prophet Joseph Smith, that “there are no angels who minister to this earth but those who do belong or have belonged to it.” Hence, when messengers are sent to minister to the inhabitants of this earth, they are not strangers, but from the ranks of our kindred, friends, and fellow-beings and fellow-servants. The ancient prophets who died were those who came to visit their fellow creatures upon the earth.  They came to Abraham, to Isaac, and to Jacob; it was such beings-holy beings if you please-who waited upon the Savior and administered to him on the Mount. The angel that visited John, when an exile, and unfolded to his vision future events in the history of man upon the earth, was one who had been here, who had toiled and suffered in common with the people of God; for you remember that John, after his eyes had beheld the glories of the great future, was about to fall down and worship him, but was peremptorily forbidden to do so. “See thou do it not; for I am thy fellow-servant, and of thy brethren the prophets, and of them which keep the sayings of this book....”
    In like manner our fathers and mothers, brothers, sisters and friends who have passed away from this earth, having been faithful, and worthy to enjoy these rights and privileges, may have a mission given them to visit their relatives and friends upon the earth again, bringing from the divine Presence messages of love, of warning, or reproof and instruction, to those whom they had learned to love in the flesh. And so it is with Sister Cannon. She can return and visit her friends, provided it be in accordance with the wisdom of the Almighty. There are laws to which they who are in the Paradise of God must be subject, as well as laws to which we are subject. It is our duty to make ourselves acquainted with those laws, that we may know how to live in harmony with his will while we dwell in the flesh, that we may be entitled to come forth in the morning of the first resurrection, clothed with glory, immortality and eternal lives, and be permitted to sit down at the right hand of God, in the kingdom of heaven.
    And except we become acquainted with those laws, and live in harmony with them, we need not expect to enjoy these privileges; Joseph Smith, Hyrum Smith, Brigham Young, Heber C. Kimball, Jedediah M. Grant, David Patten, Joseph Smith, Sen., and all those noble men who took an active part in the establishment of this work, and who died true and faithful to their trust, have the right and privilege, and possess the keys and power, to minister to the people of God in the flesh who live now, as much so and on the same principle as the ancient servants of God had the right to return to the earth and minister to the Saints of God in their day. (Gospel Doctrine, p.435)

Bruce R. McConkie
    These messengers, agents, angels of the Almighty, are chosen from among his offspring and are themselves pressing forward along the course of progression and salvation, all in their respective spheres.(Mormon Doctrine, p. 35)