Imam Ali (AS) said:

O’ people, ask me about any subject except issues which are exclusive to God and I will give you all the answers; and after me anyone else claims such a thing is either ignorant or a liar. Suddenly a man who seemed to be a Jewish Arab stood up and in a disrespectful manner told Imam Ali (AS): O’ the one who claims a thing which you have no knowledge of! And you undertake something which you cannot understand its depth! I have a question, can you answer me? The companions of Imam Ali (AS) became uneasy and decided to teach this impolite person a lesson, but Imam (AS) stopped them and said: Leave him alone, do not rush because this will stop God’s Proves to prevail. Then looked at that man and said: Ask whatever you want and say whatever is in your heart. That man asked his questions and Imam Ali (AS) answered all of them, and then that man shook his head and converted to Islam and became one of the devoted followers of Imam Ali (AS) [1].

[1] Beharul Anwaar, Vol. 57, Page 231.

Source: en.shafaqna.com