Keys as instructions

"They were so sacred that when Heber C. Kimball wrote to fellow apostle Parley P. Pratt just a few weeks later, he said that Joseph had taught them some precious things on the priesthood that would cause his soul to rejoice if he knew them, but that Joseph had given instructions that these keys not be written about. Heber concluded his description of the newly revealed endowment by saying that Parley would have to come to Nauvoo to receive the instruction for himself." (Letter of Heber C. Kimball to Parley P. Pratt, 17 June 1842, Church Archives, The Words of Joseph Smith)