What are the proofs, not taken from the Quran, for the truth of the Quran and the existence of Islam and the Prophet Muhammad?

The existence of Islam, the revelation of the Quran, and the prophethood of Muhammad (peace be upon him) are conclusive and widely attested facts. The proofs of the Prophet's truthfulness (peace be upon him) are clearer than the sun. He challenged with the Quran, and it was a miracle. Allah supported him with victory and triumph. Muslim scholars have debated with the People of the Book. In a debate between Ibn al-Qayyim and a prominent Jewish scholar, Ibn al-Qayyim explained to him that their denial of Prophet Muhammad (peace be upon him) implies an insult to Allah Almighty. How could Allah support and endorse someone who falsely and unjustly claims prophethood? This is unbecoming of Allah. This compelled the scholar to admit Muhammad's prophethood (peace be upon him), but he claimed that he was sent only to the unlettered. Ibn al-Qayyim refuted this claim by asserting that the Prophet (peace be upon him) was sent to all mankind and fought the People of the Book, inviting them to Islam. Furthermore, other holy scriptures contain indications of Muhammad's prophethood (peace be upon him).