I have read one of your recent articles and I wanted to know, what is the legal requirement for someone to be considered a knowledgeable scholar whom we can take knowledge from? Is Isnad (chain of transmission) one of the requirements and is there any evidence for this deduced from the sources?
Also, I have noticed that Isnad is not usually mentioned by the scholars as a prerequisite for someone to be considered a Mujtahid. Can one therefore be self taught?