Imam Hassan Askari (as) and philosopher Ishaq al-Kindi:

Our 11th Imam, Imam Hassan Askari (as) lived a short life of 28 years.
In this short life, Imam Hassan Askari (as) had to endure great
sufferings at the hands of the Abbasid Caliphs. But in spite of all
that suffering and confinement in Samarra, Iraq, many students
benefited from his God gifted knowledge and later became scholars in
their fields. Imam Hassan Askari (as) discussed with agnostics of that
age many times about the existence of God and the reasons for the
necessity of the Prophets and Imams and many atheists changed their
minds and converted to Islam.
One of those was Ishaq al-Kindi. This man was a great philosopher of
Iraq. He collected such verses of Noble Qur'an whose meanings were
apparently contradictory, in a book called as "self-contradictions".
He wanted to prove thereby that it was not the word of Almighty Allah
(SWT).
When the news reached Imam Hassan Askari (as), he waited for an
opportunity to refute him. One day, by chance some of his disciples
(students) came to Imam Hassan Askari (as).
Imam Hassan Askari (as) asked them: "Is there anyone among you who can
stop Ishaq al-Kindi from wasting his time in this useless effort
fighting the Noble Qur'an?" The students said: "Sir, we are his
students: how can we object to his teaching?" Imam Hassan Askari (as)
urged that they could at least convey to their teacher what he had to
tell them. They replied that they would be ready to cooperate as much
as they could in that respect.
Imam Hassan Askari (as) then recited a few verses from the Noble
Qur'an, which the philosopher Ishaq al-Kindi thought as contradictory
of one another. Imam Hassan Askari (as) then explained to them thus:
"Your teacher thinks that some of the words in these verses have only
one meaning. But according to the Arabic language, these words have
other meanings too which, when taken into consideration, indicate no
contradiction in the overall meaning. Thus, your teacher is not
justified for basing his objections and claim of contradictions on the
premises of the 'wrong meaning' he himself selects such verses". Imam
Hassan Askari (as) then put up some examples of such words before them
so clearly that the students conceived the whole discussion and the
precedents of more than one meaning.
When these students visited Ishaq al-Kindi and after routine talk,
reproduced the disputed points, he was surprised. He was a fair-minded
scholar and he listened to his students' explanations. Then he said:
"What you have argued is beyond your capacity: tell me truly who has
taught you these points?" The students said that it was their own
reflection, but when he insisted that they could never have conceived
those points, they admitted that, it was explained to them by Abu
Muhammad Imam Hassan Askari (as). The teacher said: "Yes: this level
of knowledge is the heritage of that House and only that House Ahlul
Bayt (as)". Then he asked the students to set fire to all such works
of his.
Ishaq al-Kindi was not alone in benefiting from Imam Hassan Askari
(as). Several high-ranking scholars benefited from his ocean of
knowledge. There were a host of others who later developed into
leading scientists, jurisprudents, exegetes, theologians and masters
of different fields when they came into contact with Imam Hassan
Askari (as).