Is it permissible for a Muslim with little Sharia knowledge to enjoin good and forbid evil? And is it permissible for him to convey the summary of a fatwa from a trusted sheikh without mentioning the Sharia evidence?

Knowledge is a prerequisite for enjoining good and forbidding evil, because the Sharia is the scale that determines what is good and what is evil. Among the levels of knowledge is knowing the sayings of scholars. There is no harm in transmitting and disseminating the fatwas of trusted scholars if their attribution is confirmed to be accurate and their content is not distorted. It must be noted that legitimate matters of scholarly difference are not occasions for censure, but rather an area for mutual advice and guidance.