For Whom is it Obligatory to Call to Allâh?

Question :

Is calling to Allâh an obligation on every male and female Muslim, or is it only compulsory for scholars and students of knowledge to do so?

Answer:

When a person has insight into what he is calling to, then there is no difference whether he is a great and famous scholar, a serious student of knowledge, or an average person, as long as he has certain knowledge about the issue. Indeed, the Messenger of Allah said:
"Convey (to others) from me, even if it is a single Verse."

So, it is not a condition that the Da'iyah (caller) have reached a great level of knowledge, but he must be knowledgeable about what he is calling to.

As for the case of someone standing up out of ignorance to call to something merely because he is emotionally charged about it, this is not allowed.

We have seen many brothers who call to Allâh who have but a little knowledge. We find them, out of their strong feelings, forbidding what Allâh did not make unlawful, and they make compulsory that which Allah did not make compulsory for His servants. This is indeed a grave mistake. This is because prohibiting what Allah allows is like allowing what Allah prohibited. So, the two are the same, one rebukes another, making something lawful, while the other rebukes them, making it prohibited. Indeed Allâh considers these the same, He said:
"And say not concerning that which your tongues put forth falsely: "This is lawful and this is forbidden, so as to invent lies against Allah. Verily, those who invent lies against Allah will never prosper. A passing brief enjoyment (will be theirs), but they will have a painful torment."

Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 8 Pages 32-33