Imam Reza (as) - Knowledge

Abū Ismā‘il al-Sindi has reported: “When I was in India, I heard that Allah had an Arab proof, so I went out to seek him. I was guided to al-Ridā (peace be on him), and I went to him. I could not speak Arabic. I greeted him in Sindi, and he greeted me in my own language. I asked him in Sindi, and he answered me in it. I said to him: ‘I have heard that Allah has an Arab argument, and I have gone out to seek him. He, peace be on him, said to me: ‘It is I; ask (me) about whatever you desire.’ I asked him about my questions, and he (peace be on him) answered them in my own language. (  Al-Majjlisi,  Bihār al-Anwār, vol. 12, p. 15. )

Reference :The life of Imām'Ali Bin Mūsā al-Ridā