Hazrat Ibn Abbas (may Allah be pleased with them) narrates that indeed the Messenger of Allah (peace and blessings be upon him) used to complete a recitation of the Holy Qur'an once every Ramadan, except for the year in which he (peace and blessings be upon him) passed away. In that year, he (peace and blessings be upon him) completed the recitation twice in the presence of Hazrat Abdullah bin Mas'ud (may Allah be pleased with him): thus, he knew which verse was abrogated and which verse was changed.