What is the ruling on one who takes the lead in da'wah (calling others to Islam) or issuing fatwas without knowledge?

Question : We see Yahya, what do you have? And let the witness convey the verse, like this hadith and like his saying

Answer : Yes. I mean, some people cite such hadiths. A worker who has only heard one hadith, the caller narrates it to the people. This is the methodology of Shaykh Salim.
No, it is not bad; he conveys only what he heard. On the condition that he has knowledge, perhaps it was copied.
So it is necessary; I hold that no one should call to Allah except with something he is certain of. That is one point. Second, if questions are directed after the sermon, he should not answer except about what he is certain of. He should not say, "I have now become a Shaykh, so ask me about whatever you wish."
He says, in the language of his state, that he begins everything by saying, "O Shaykh, this is haram (forbidden), that is not haram, that is wajib (obligatory), that has a distinction." You see, some of the ignorant are in this state. Yes, this is the state. It is not permissible. If you are asked about something you know as clearly as the sun, answer. Otherwise, say, "By Allah, my brother, I have no knowledge of this, so ask about it." This clears your conscience, and it is known that you are a cautious man, and you will be rewarded more from it.