Is it permissible for common people to issue fatwas to others regarding matters of lawful and unlawful, and what is the way to advise them?

It is encouraged for the ignorant person to ask about what he does not know concerning the rulings of Islamic law, and it is incumbent upon the scholar to answer. It is not permissible for one who has no knowledge to delve into the religion of Allah without knowledge, lest he fall into the forbidden act that Allah has prohibited, as He says: "Say, 'My Lord has only forbidden immoralities – what is apparent of them and what is concealed – and sin and oppression without right, and that you associate with Allah that for which He has not sent down authority, and that you say about Allah that which you do not know.'" And Allah Almighty says: "And do not say about what your tongues falsely describe, 'This is lawful and this is unlawful,' to invent falsehood about Allah. Indeed, those who invent falsehood about Allah will not succeed. [Enjoy] a brief pleasure, and they will have a painful punishment."