It is narrated from Hazrat Amr bin Aas (may Allah be pleased with him) that once he heard a man reciting a verse of the Holy Qur'an, so he asked him, "Who taught you this verse?" He replied, "The Prophet (peace and blessings of Allah be upon him) did." He said, "The Prophet (peace and blessings of Allah be upon him) taught me this verse in a different way." So both of them went to the presence of the Prophet (peace and blessings of Allah be upon him). One of them referred to the verse and recited it. The Prophet (peace and blessings of Allah be upon him) said, "This verse was revealed in this way." The other recited it according to his own way and said, "O Messenger of Allah (peace and blessings of Allah be upon him), was this verse not revealed in this way?" The Prophet (peace and blessings of Allah be upon him) said, "It was revealed in this way as well." Then he said, "This Holy Qur'an has been revealed upon seven letters. Whichever letter you recite according to, you will recite correctly. Therefore, do not dispute in the Holy Qur'an, for disputing in the Qur'an is disbelief."