Who are the scholars from whom knowledge can be taken, and what are their conditions? Is it necessary for them to be well-known and vouched for?

A scholar is one who knows true knowledge with its evidence, whether his knowledge is broad or specialized in a single issue, and his mission is to convey what he has learned with evidence. Preachers, even if they offer some benefit, are not qualified to receive religious knowledge unless their statements are based on sound evidence from the Qur'an and Sunnah. Ibn Mas'ud warned against reciters without fiqh (understanding), and what is meant by fiqh is that a person has wisdom in placing matters in their proper contexts, and that his evidence is a proof for him before Allah. The commendation of scholars is not a prerequisite for the permissibility of teaching people or issuing fatwas for someone who knows the truth with its evidence and is qualified for it, but it is among the means by which a scholar is recognized and trusted.