What is the response to a person who claims to be a Muslim yet doubts the truthfulness of Allah Almighty in His promises and the authenticity of the Prophetic hadiths, and how can we respond to him without citing the Holy Quran?

Belief in Allah's promise and warning, which are firmly established in the Qur'an and Sunnah, is among the requirements of faith. Allah Almighty has sworn to fulfill His promise and warning. Allah's promise and warning have frequently materialized in this world, as He destroyed nations due to sins and honored nations due to obedience.

Among the greatest proofs of the Prophet's truthfulness (peace and blessings be upon him) is the fulfillment of his prophecies, such as the appearance of the Hijaz fire, which illuminated the necks of camels in Busra, and which occurred in the year 654 AH, as the Prophet (peace and blessings be upon him) informed, and historians bore witness to this. The Companions and the righteous predecessors believed the Messenger of Allah (peace and blessings be upon him) in all that he reported, such as the incident of Al-Isra' (the Night Journey). The Hadith scholars were meticulous in accepting narrators, only accepting narrations from reliable and precise individuals with an unbroken chain of transmission.