Know that in the same way that backbiting is forbidden for the one who speaks it, it is likewise forbidden for the one who listens to it and approves of it.

Thus, it is obligatory on the one who hears an individual embarking on committing the prohibited form of backbiting, to forbid him from doing it as long as he does not fear any open harm resulting from that. But if he does fear (harm) from that, then he is obligated to reject the backbiting with his heart and to detach himself from that gathering if he is able to do so. If he has the ability to reject it with his tongue or to cut the backbiting off by changing the topic, then that becomes required of him. And if he does not do that, then he has committed an act of disobedience (i.e. sinned).[url][/url]https://abdurrahman.org/2015/04/26/the-sin-of-listening-to-the-backbiting-and-not-prohibiting-it-imam-nawawi/