Nephi noted that “there was not any man who could do a miracle in the name of Jesus save he were cleansed every whit from his iniquity” (3 Nephi 8:1; see also D&C 121:36).
The following story told by Elder Vaughn J. Featherstone while serving in the Presiding Bishopric illustrates the need for priesthood holders to be pure at all times:
“People cannot hide sin. You cannot mock God and hold the Lord’s holy priesthood and pretend to propose that you are his servant.
“I know of a great man who held his dead son in his arms, and said, ‘In the name of Jesus Christ and by the power and authority of the Holy Melchizedek Priesthood, I command you to live.’ And the dead boy opened up his eyes.
“This great brother could not have possibly done that had he been looking at a pornographic piece of material a few nights before or if he had been involved in any other transgression of that kind. The priesthood has to have a pure conduit to operate” (in Conference Report, Apr. 1975, 100; or Ensign, May 1975, 66).
Elder Jeffrey R. Holland of the Quorum of the Twelve Apostles explained that although not every priesthood administration will result in a miraculous event, only those who are worthy can perform miracles in the name of Christ. Priesthood holders must keep themselves pure and clean: “Now, my young friends of both the Aaronic and Melchizedek Priesthood, not every prayer is answered so immediately, and not every priesthood declaration can command the renewal or the sustaining of life. Sometimes the will of God is otherwise. But young men, you will learn, if you have not already, that in frightening, even perilous moments, your faith and your priesthood will demand the very best of you and the best you can call down from heaven. You Aaronic Priesthood boys will not use your priesthood in exactly the same way an ordained elder uses the Melchizedek [Priesthood], but all priesthood bearers must be instruments in the hand of God, and to be so, you must, as Joshua said, ‘sanctify yourselves’ [Joshua 3:5]. You must be ready and worthy to act” (in Conference Report, Oct. 2000, 51; or Ensign, Nov. 2000, 39).