Is it permissible for my friend to continue speaking on the phone with a Sheikh, even if it's not always for religious questions, knowing that his wife is bothered by it and that the Sheikh encourages her on the pretext that no wrong is being committed and they are not seeing each other?

Questions must be serious and clear, and answers concise and brief. A woman must not speak in a soft, alluring manner, as Allah Almighty says: "Then do not be soft in speech [to men], lest he in whose heart is disease should covet, but speak with appropriate speech."

So, if her voice is something that listeners might find pleasurable or from which temptation is feared, then it is forbidden to listen to it.

We advise against continuous conversations between a woman and a sheikh, fearing temptation. A woman should remember that she is a stranger to this sheikh, so she should limit herself to essential questions or ask other sheikhs whose piety, knowledge, and devoutness are trusted, especially since the sheikh's wife is bothered by these conversations.