How can one respond to attempts to cast doubt on the authenticity of the Quran and claims of its distortion, especially given the existence of an alleged Yemeni copy that shows differences from the commonly circulated Quran?

The authenticity of the copies of the Holy Quran has been proven by much evidence, including its preservation in hearts and in written form across generations, its transmission along with its exegesis and the reasons for its revelation, its challenge through foretelling the unseen, and the consistency of its copies around the world. Unknown copies that claim distortion are of no value, as manuscript copies are subject to strict rules for proving their authenticity. The story of the Jew who tried to distort the Torah, the Gospel, and the Quran indicates its preservation; he succeeded in distorting the first two, but a Muslim bookseller discovered his distortion of the Quran, and even Muslim children can detect any error in it.