How can a couple atone for breaking the fast by engaging in sexual intercourse in heat of passion? I was not sure whether an intercourse is allowed during fasting or not. Initially my wife had I had a feeling that it was Ḥalāl. Later on, the following day, my wife and I read that it was Ḥarām and we have to pay Kaffara for the action we had committed. Can we just pay fidyah for the broken fast?
The Prophet [pbuh] did not specify a definite expiation. His decision on a similar case follows:
A man came to the Prophet (sws). He said: "I have been ruined, O Messenger of God!" The Prophet (sws) asked him what had ruined him. The man replied: "I have had sexual intercourse with my wife while fasting." The Prophet (sws) asked him whether he had something to buy a slave his freedom. The man replied in the negative. The Prophet (sws) then asked him if he could continuously fast for two months. He again replied in the negative. The Prophet (sws) asked him whether he could feed sixty needy people. He again replied in the negative. Then he sat there. Meanwhile, a basket full of dates was presented to the Prophet (sws). The Prophet (sws) asked him to give away the basket of dates in the way of Allah. At this, he said: "Who would need these more than me! There is no house between these two barren plains of Madīnah needier of these dates than mine." At this the Prophet (sws) smiled such that his teeth could be seen. Then the Prophet (sws) said to him: "Go and feed your family with these." (Muslim, No: 1111)
The wording of a variant transmitted on the authority of 'Ᾱ'ishah (rta) follows:
The Prophet (sws) said to him: "Give in charity, give in charity." The man explained that he had nothing to give away. Then the Prophet (sws) commanded him to stay there. Then two baskets of food were presented to the Prophet (sws) who commanded the man to give those baskets of food in charity. (Muslim, No: 1112)
I believe you can just repeat the fast later on and do some act of charity if possible. As for the fidyah for leaving the fast please note that this option is no more possible. The Holy Qur'an itself has clarified that it is necessary to repeat the fasts when one is healthy.