What is the evidence that the Quran has been preserved against distortion?

All perfect praise be to Allaah, The Lord of the Worlds.  I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Evidence of the preservation of the Quran against distortion is found in the verse (which means): {Indeed, it is We who sent down the Quran and indeed, We will be its guardian.}[Quran, 15:9] The Quran, according to consensus of the Muslim scholars has been integrally preserved against all kinds of distortion. Anyone who claims the contrary is considered a disbeliever.

Also, please refer to Fataawa 87819 and 91552 for further details.

Allaah Knows best.