Reference: Fataawa Ramadhaan v2 p612 no.608
Fataawa as-Siyaam libni Jibreen p69
Question: I had sexual intercourse with my wife during the day in Ramadhaan. I was not aware that it was the first day of Ramadhaan and nor did many other people until after the ‘Asr prayer so do I [now] have to make an expiation?
Response: There is nothing required of you except to make up the fast that you missed and there is no expiation to make. This is because you did not know that it was the first day of Ramadhaan so you did not violate the sanctity of the day of Ramadhaan intentionally.
