Angels Sent to Perform Labors
Only Angels Can Do

Wilford Woodruff
    I said to him that if he were to pray a thousand years to the God of Israel for that gift, it would not be granted, unless the Lord had a motive in sending an angel to him. I told him that the Lord never did nor never will send an angel to anybody merely to gratify the desire of the individual to see an angel. If the Lord sends an angel to anyone, He sends him to perform a work that cannot be performed [except] by the administration of an angel. (Deseret Weekly News, 53:642-43)

Joseph Fielding Smith
    It is contrary to the law of God for the heavens to be opened and messengers to come to do anything for man that man can do for himself. (Doctrines of Salvation, 1:196).