Is it permissible for a husband to allow his wife to attend lessons of knowledge at the mosque, knowing that the lesson might end an hour after 'Isha prayer, and that she will return home accompanied by trustworthy sisters and will not use public transportation alone?

If the wife is safe from dangers and in reliable company, and she avoids religious prohibitions such as immodest display (tabarruj) and free mixing, then there is no objection to the husband allowing his wife to attend gatherings of goodness and lessons of knowledge. Rather, it is preferable due to the need of the female community for knowledge. However, the husband is not obligated to permit her unless what she will learn is an obligation upon her and he is not teaching her. The jurists have agreed on the prohibition of a wife leaving her home without her husband's permission, except out of necessity or an urgent need, such as fear for herself or her property, seeking justice from a judge, or for learning or seeking a fatwa (definition) if a trustworthy husband does not suffice her. Attending lessons of knowledge is not a necessity that permits leaving without the husband's permission, unless it is obligatory upon her.