D&C 20

As the Church was being organized, the Lord said -

"After it was truly manifested unto this first elder that he had received a remission of his sins, he was entangled again in the vanities of the world;
6 But after repenting, and humbling himself sincerely, through faith, God ministered unto him by an holy angel, whose countenance was as lightning, and whose garments were pure and white above all other whiteness;
7 And gave unto him commandments which inspired him;
8 And gave him power from on high..."  (Doctrine and Covenants | Section 20:5 - 8)

This has to provide a great deal of confidence for all that have been called to the work, with all the inadequacies and feelings of unworthiness, that they to can repent and be sustained in their calling.