Who are those who transmitted to us the existence and biography of the Prophet (peace be upon him)?

The biography of the Messenger, peace and blessings be upon him, and his narratives have reached us through continuous transmission via frequently narrated chains of narrators (mutawatir isnads), and our Ummah is distinguished by the characteristic of isnad (definition). As for the whispers concerning the distortion of the Qur'an, one must completely disregard them, for the Qur'an is preserved from alteration and change by the words of Allah Almighty: "Indeed, it is We who sent down the Dhikr (the Qur'an), and indeed, We will be its Guardian." The cure for these whispers is to completely ignore them and believe that they are a satanic thought, and combating them is considered a jihad against the enemy of Allah.