The Messenger of Allah ﷺ said one day in his sermon, "Indeed, my Lord has commanded me to teach you what you do not know from what He has taught me this day of mine."He also said, "I have only sent you to test you and to test others through you, and I have revealed to you a Book which water cannot wash away, which you recite whether asleep or awake." The hadith continues.
أن رسول الله ﷺ قال ذات يوم في خطبته: ألا إن ربي أمرني أن أعلمكم ما جهلتم مما علمني يومي هذا… وقال: إنما بعثتك لأبتليك وأبتلي بك وأنزلت عليك كتابا لا يغسله الماء تقرؤه نائما ويقظان. الحديث.
Muslim narrated it in the Book of Paradise and the Description of Its Bliss (2865), through several chains, from Muaz bin Hisham, who said, my father narrated to me, from Qatada, from Mutarrif bin Abdullah bin Shikhir, from Iyad bin Himar Majashi, and he mentioned it.His saying, "water does not wash it away," means that the Quran will never disappear from the earth. Rather, it will remain preserved in hearts and in writing until the Day of Resurrection, without distortion or alteration. This is one of the distinguishing features of the noble Quran. As for the scriptures of other religions, although they still exist, they have been distorted, and the distortion within them has continued ever since.His saying, "whether asleep or awake," is addressed to the Prophet ﷺ, for the Quran is the same to him whether he is asleep or awake, and this is one of the distinguishing features of the Prophet ﷺ.