Gershom Bar Razah wrote:
 We see, then, that Adam did not want to give Eve the exact words he received, but he added [ibid. iii. 3]: "Ye shall not eat of it, neither shall ye touch it, lest ye die," in order that they should take care even not to touch the tree. 
According to Rashi, Eve said those words, not Adam, and thereby diminished God's words by adding to them.