Reference: Fataawa Ramadhaan – Volume 2, Page 609, Fatwa No.602
al-Muntaqaa min Fataawa Shaykh Saalih ibn Fowzaan – Volume 3, Page 136
Question: A man had sexual intercourse with his wife during the day in Ramadhaan, over a period of three consecutive days. What is required of him and may Allaah reward you?
Response: If one has sexual intercourse [during the day in Ramadhaan] whilst fasting, then he (/she) has committed a great sin. It is obligatory upon him (/her) to repent to Allaah for this and make up the fast for the day[s] in which he (/she) had sexual intercourse.
In addition to this, he (/she) is required to pay a penalty (kaffaarah) which involves freeing a slave and if he (/she) is unable to find one, then to fast two consecutive months and if he (/she) is unable to do so, then to feed sixty poor and needy people; and for each one is half a saa’ of food. And the penalty (kaffaarah) recurs according to the number of days on which he (/she) had sexual intercourse.
And Allaah [alone] has the Complete knowledge [of all affairs].