If you argue with them and tell them that God is One...

If you argue with them and tell them that God is One, they would say, `Prove His Oneness,' and if you say that Muhammad (S) is the Messenger of God, they would say, `Confirm his Message,' then they would press their lies on a person while he tries to disprove their lies, and they would continue to prove that he is mistaken till he abandons his argument; so, beware of them, may my life be sacrificed for you." He smiled and asked, "O Nawfali!

Do you fear that they will disprove my argument?" He answered, "No, by God! I have never worried about you, and I hope God will enable you to have the upper hand over them." The Imam asked again, "O Nawfali!

Would you like to know when al-Ma’mun will feel regretful?" He answered, "Yes." He said, "When he hears me argue with the people of the Torah quoting their own Torah, with the people of the Gospel (Bible) quoting their own Gospel, with the people of the Psalms quoting their own Psalms, with Zoroastrians arguing in their Persian language, with the Romans in their own Latin, and with rhetoricians using their very rhetoric.

So, if I closed all the avenues of argument in the face of each arguing party and disproved his claim, making him renounce his statement from its onset and referring to my own statement, then al-Ma’mun would know that he would not achieve what he aspires.

It is then that he will feel regretful; We are God's, and Unto Him is our return ." Thus does the Imam show that he was taking lightly and was not concerned about such persons whom al-Ma’mun wished to gather together against him trying to embarrass him with their falsification and arguments which he hoped might close for the Imam (a.s.) all the avenues of argument.

When the session starts and the Imam (a.s.) is invited to join it, discussion starts and the Imam (a.s.) starts his debate with the Catholics, making the Bible his reference to prove his own defense of the Unity of God and disprove the Godhead of Christ (a.s.) by those who regarded him as a god besides God.

Then he follows with a magnificent discussion proving that the Bible in circulation today is not the same which God had revealed to Christ (a.s.) and that it is authored by some of the disciples of Jesus (a.s.) who are the authors of the four gospels, depending in his argument on the fact that the details presented by each one of them stand in flagrant contradiction with those of the other.