Jasliq was a great scholar of the Christians, and he used to have debates with Islamic scholars. He used to say: The Muslims and we both agree on the prophethood of Isa (a.s) and that his book is a heavenly scripture. Also that he is alive in the heavens. The disagreement is over the prophethood of Muhammad al-Mustafa. They believe in it and we do not. But we both agree that he has died. Thus when he is no more, what is the use of his prophethood? On the contrary, since Isa is alive, it is necessary to believe in his prophethood. Most of people who heard these statements were unable to refute him.
Once, this man came to Imam (a.s) upon the instructions of Mamun and began the conversation thus:
Jasliq: First tell me whether you believe in Isa (a.s) and his book or not? Imam: I have faith in the prophethood of that Isa who gave glad tidings to his companions regarding the prophethood of Muhammad al-Mustafa. And I testify that Taurat, which mentions this good news. But I have no faith in the Isa who does not confess the prophethood of the Seal of the Prophets and that book which does not mentions it. As soon as he heard these words, Jasliq became speechless.
Then Imam (a.s) said, “We believe Isa to be a true prophet who gave glad tidings of the prophethood of Muhammad al-Mustafa. However, you make him defective and consider him to be needful of Prayers and fasting.” He asked, “What does that mean?” Imam replied, “When in your belief, he is God himself (we seek Allah’s refuge!), for whom did he pray and fast?” Jasliq could not offer any reply. After some time he said, “If he were not God, how did he enliven the dead, cure the lepers and give vision to the blind? Who can do this besides God?”
Imam said, “This was not restricted to only Isa (a.s). It was found in other prophets also. Al Yasa (a.s) used to walk on water and cure the blind and the lepers. Prophet Hizqil (a.s) made 35000 people alive after they were dead for sixty years. Prophet Ibrahim (a.s) made the birds alive. By the prayers of Prophet Musa, seventy people became alive on Mount Tur. In the same way, many people became alive after dying, due to the prayers of Prophet Muhammad al-Mustafa. Are all these prophets deserving of Godhood, according to your belief?” Hearing all this, Jasliq fell silent and at last accepted Islam.
Reference :Akhlaq al-A’imma, Morals & Manners of the Holy Imams