Imam Reza (AS) employed a variety of methods when using Quranic verses in his arguments. Sometimes, he would clarify the apparent and hidden meanings of the verses through precise interpretation, responding to doubts raised about the Quran. On other occasions, he would prove the truth of Quranic prophecies by relating the verses to historical events.
By relying on the unequivocal verses (Muhkamat) of the Quran, Imam Reza (AS) explained the ambiguous verses (Mutashabihat) and addressed some of the doubts raised against Islam.
Additionally, in his discussions with followers of other divine religions, he would refer to verses present in their scriptures as well. For instance, he would reference the oneness of the origin and purpose of religions, citing the sacred books of other faiths.
Imam Reza (AS), through the use of Quranic verses, provided proofs for the oneness and unity of God, rejected polytheism and idolatry, discussed the afterlife and resurrection, proved the prophethood of divine messengers, particularly Prophet Muhammad (PBUH), and their miracles, as well as the Imamate and guardianship of the Ahl al-Bayt (AS). He also explained Islamic laws and regulations, addressing any doubts in these areas.
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For example, one objection raised during a debate with a Christian scholar was that Prophet Muhammad (PBUH) could not be a prophet because his holy book was not in Hebrew. Imam Reza (AS), citing the verse “We did not send any apostle except with the language of his people, so that he might make [Our messages] clear to them” (Surah Ibrahim, verse 4), emphasized that God sends prophets with the language of their people so that the divine message can be best understood by them. Since the Arabs were the primary audience of the Prophet (PBUH), the Quran was revealed in Arabic. This book is a great miracle, and even if it were not in Arabic, it could still be a divine book. However, God revealed it in Arabic to convey His message in the best possible way to the Arabs.