You Need An Endowment, Brethren...And Those That Reject Your Testimony Will Be Damned.

You need an endowment, brethren, in order that you may be prepared and able to overcome all things; and those that reject your testimony will be damned. The sick will be healed, the lame made to walk, the deaf to hear, and the blind to see, through your instrumentality. But let me tell you, that you will not have power, after the endowment to heal those that have not faith, nor to benefit them, for you might as well expect to benefit a devil in hell as such as are possessed of his spirit, and are willing to keep it: for they are habitations for devils, and only fit for his society.But when you are endowed and prepared to preach the Gospel to all nations, kindreds, and tongues, in their own languages, you must faithfully warn all, and bind up the testimony, and seal up the law, and the destroying angel will follow close at your heels, and exercise his tremendous mission upon the children of disobedience; and destroy the workers of iniquity, while the Saints will be gathered out from among them, and stand in holy places ready to meet the Bridegroom when he comes.

Joseph Smith, History of the Church 2:309