What are the reasons for the proliferation of preachers whose source of knowledge is unknown, and why do some of them issue extremist fatwas or not adhere to the asceticism they preach, and how can one distinguish between the pious, learned sheikh and the sheikh who exploits religion?

The default is to think well of callers to Islam and seekers of knowledge, and to interpret their words and actions in the best possible light. One must beware of thinking ill of them and accusing them of wrongdoing without clear evidence. Asceticism does not necessitate abandoning permissible things. What matters is the state of the heart and its attachments; a wealthy person might be more ascetic than a poor, covetous one. Perfection is rare, and a wise person benefits from what a scholar possesses, and is not deterred by their slips. Growing a beard is obligatory for adults and youth, and there is no special concession for young people in this regard.