Reference: Fataawa Ramadhaan – Volume 2, Page 624, Fatwa No.624
Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-‘Ilmiyyah wal-Iftaa. – Fatwa No.13432
Question: A man returned home from a journey and had not been fasting [due to his travels, so he] decided [now he was at home] to fast [the rest of the remaining day]. He then found his wife taking a bath [since she had] completed her menses; Is it permissible for him to have sexual intercourse with her in this case or should they both assume the fast for the [remainder of the] day?
Response: If he arrived [home] from his journey in Ramadhaan, then he is required to fast [the remainder of the day] and it is not permissible for him to have sexual intercourse with his wife on the day of his return, out of respect for the sanctity of the month of Ramadhaan.
And with Allaah lies all the success, and may Allaah send prayers and salutations upon our Prophet Muhammad ﷺ and his family and his companions.
