Is it permissible for a woman to pray a supererogatory prayer with her husband who is praying a fard (obligatory) prayer, adducing as evidence the hadith: "Who will be charitable to this one?"

A wife re-praying with her husband to attain the reward of congregational prayer is a good deed. If one of you prays in his dwelling and then finds the Imam (at the mosque) has not yet prayed, he should pray with him, for it will be a supererogatory (nafila) prayer for him. It is preferable for them to pray together if the husband is unable to go to the mosque due to a legally valid excuse. However, if the husband is able to go to the mosque but does not, then he is sinful.