All perfect praise be to Allah, The Lord of The Worlds, and may his peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
It is forbidden for a fasting person to discharge semen deliberately by engaging in foreplay with wife, even without insertion. Doing so renders his fast invalid, and he is considered sinful and should make up for the fast of that day.
Al-Imam An-Nawawi said: "If the husband engaged in foreplay with wife, and ejaculated, or he kissed her and ejaculated as a result then his fast is void, but if he didn`t ejaculate then his fast is valid."{Al-Majmou`}.
As regards the wife, it forbidden for her to allow him to do so, but if she couldn`t stop him then she isn`t sinful, and if she had no ejaculation, nor satisfied her sexual desire then her fast is valid and she doesn`t have to make up for the fast of that day.
As regards the husband, he should make repentance, seek forgiveness, and make up for that missed day if he ejaculated without insertion. And Allah Knows Best.
