There are many sound hadiths related to this, such as the hadith of Hakim ibn Hizam (Allah be pleased with him), in which the Messenger of Allah (Allah bless him and give him peace) said,
Do not touch the Quran unless you are in a state of purity. [Related by Imam Malik in his Muwatta, and deemed sound by early and late hadith authorities, such as Imam Nawawi in his Majmu']
http://spa.qibla.com/issue_view.asp?HD=1&ID=2618&CATE=32
EDIT: Replaced touch by Read cuz he read it..