D&C 50

The Lord asked several inquiring Elders - 

"...unto what were ye ordained?"  (Doctrine and Covenants 50:13)

To that question, the Lord answered - 

"To preach my gospel by the Spirit, even the Comforter which was sent forth to teach the truth.

15 And then received ye spirits which ye could not understand, and received them to be of God; and in this are ye justified?

16 Behold ye shall answer this question yourselves; nevertheless, I will be merciful unto you; he that is weak among you hereafter shall be made strong.

17 Verily I say unto you, he that is ordained of me and sent forth to preach the word of truth by the Comforter, in the Spirit of truth, doth he preach it by the Spirit of truth or some other way?

18 And if it be by some other way it is not of God.

19 And again, he that receiveth the word of truth, doth he receive it by the Spirit of truth or some other way?

20 If it be some other way it is not of God.

21 Therefore, why is it that ye cannot understand and know, that he that receiveth the word by the Spirit of truth receiveth it as it is preached by the Spirit of truth?

22 Wherefore, he that preacheth and he that receiveth, understand one another, and both are edified and rejoice together.

23 And that which doth not edify is not of God, and is darkness.

24 That which is of God is light; and he that receiveth light, and continueth in God, receiveth more light; and that light groweth brighter and brighter until the perfect day.

25 And again, verily I say unto you, and I say it that you may know the truth, that you may chase darkness from among you;

26 He that is ordained of God and sent forth, the same is appointed to be the greatest, notwithstanding he is the least and the servant of all."  (Doctrine and Covenants 50:14–26)