D&C 5

 The Lord instructs Martin Harris - 

"...I speak unto you, my servant Joseph, concerning the man that desires the witness—

24 Behold, I say unto him, he exalts himself and does not humble himself sufficiently before me; but if he will bow down before me, and humble himself in mighty prayer and faith, in the sincerity of his heart, then will I grant unto him a view of the things which he desires to see.

25 And then he shall say unto the people of this generation: Behold, I have seen the things which the Lord hath shown unto Joseph Smith, Jun., and I know of a surety that they are true, for I have seen them, for they have been shown unto me by the power of God and not of man.

26 And I the Lord command him, my servant Martin Harris, that he shall say no more unto them concerning these things, except he shall say: I have seen them, and they have been shown unto me by the power of God; and these are the words which he shall say."  (Doctrine and Covenants 5:23–26)

I think it is interesting that the Lord instructs Martin - 

"...that he shall say no more unto them concerning these things..."

Sometimes in our pride we want to tell more.  But we have to be careful to only say what we are instructed to say in our callings.